feat: solve part two

.gitignore

@@ -1 +1,2 @@
 bin/aoc
+*.test

Makefile

@@ -1,60 +1,61 @@
 GO = go
 BIN = bin/aoc
 
-.PHONY: build test clean new
+.PHONY: build test clean
 
 build:
 	@mkdir -p $(dir $(BIN))
 	@$(GO) build -o $(BIN) ./cmd/aoc
 
 test:
-	@$(GO) test ./...
+	@$(GO) test ./internal/...
 
 clean:
 	@rm -f $(BIN)
 
-new:
-	@if [ -z "$(filter-out $@,$(MAKECMDGOALS))" ]; then \
-		echo "Usage: make new 2020D9"; \
-		exit 1; \
-	fi
-	@DAY_ARG=$$(echo $(filter-out $@,$(MAKECMDGOALS)) | awk '{print $$1}'); \
-	YEAR=$$(echo $$DAY_ARG | sed 's/D.*//'); \
-	DAY_NUM=$$(echo $$DAY_ARG | sed 's/.*D//'); \
-	DAY_NAME=$$(case $$DAY_NUM in \
-		1) echo "One" ;; \
-		2) echo "Two" ;; \
-		3) echo "Three" ;; \
-		4) echo "Four" ;; \
-		5) echo "Five" ;; \
-		6) echo "Six" ;; \
-		7) echo "Seven" ;; \
-		8) echo "Eight" ;; \
-		9) echo "Nine" ;; \
-		10) echo "Ten" ;; \
-		11) echo "Eleven" ;; \
-		12) echo "Twelve" ;; \
-		13) echo "Thirteen" ;; \
-		14) echo "Fourteen" ;; \
-		15) echo "Fifteen" ;; \
-		16) echo "Sixteen" ;; \
-		17) echo "Seventeen" ;; \
-		18) echo "Eighteen" ;; \
-		19) echo "Nineteen" ;; \
-		20) echo "Twenty" ;; \
-		21) echo "TwentyOne" ;; \
-		22) echo "TwentyTwo" ;; \
-		23) echo "TwentyThree" ;; \
-		24) echo "TwentyFour" ;; \
-		25) echo "TwentyFive" ;; \
-		*) echo "Unknown" ;; \
-	esac); \
-	mkdir -p internal/$$YEAR/Day$$DAY_NAME; \
-	mkdir -p internal/data/$$YEAR/Day$$DAY_NAME; \
-	touch internal/$$YEAR/Day$$DAY_NAME/code.go; \
-	touch internal/$$YEAR/Day$$DAY_NAME/code_test.go; \
-	touch internal/data/$$YEAR/Day$$DAY_NAME/input.txt; \
-	echo "Created files for $$DAY_ARG"
-
 %:
-	@:
+	@DAY_ARG=$@; \
+	if echo $$DAY_ARG | grep -qE '^[0-9]{4}D[0-9]+$$'; then \
+		YEAR=$$(echo $$DAY_ARG | sed 's/D.*//'); \
+		DAY_NUM=$$(echo $$DAY_ARG | sed 's/.*D//'); \
+		DAY_NAME=$$(case $$DAY_NUM in \
+			1) echo "One" ;; \
+			2) echo "Two" ;; \
+			3) echo "Three" ;; \
+			4) echo "Four" ;; \
+			5) echo "Five" ;; \
+			6) echo "Six" ;; \
+			7) echo "Seven" ;; \
+			8) echo "Eight" ;; \
+			9) echo "Nine" ;; \
+			10) echo "Ten" ;; \
+			11) echo "Eleven" ;; \
+			12) echo "Twelve" ;; \
+			13) echo "Thirteen" ;; \
+			14) echo "Fourteen" ;; \
+			15) echo "Fifteen" ;; \
+			16) echo "Sixteen" ;; \
+			17) echo "Seventeen" ;; \
+			18) echo "Eighteen" ;; \
+			19) echo "Nineteen" ;; \
+			20) echo "Twenty" ;; \
+			21) echo "TwentyOne" ;; \
+			22) echo "TwentyTwo" ;; \
+			23) echo "TwentyThree" ;; \
+			24) echo "TwentyFour" ;; \
+			25) echo "TwentyFive" ;; \
+			*) echo "Unknown" ;; \
+		esac); \
+		mkdir -p internal/$$YEAR/Day$$DAY_NAME; \
+		mkdir -p internal/data/$$YEAR/Day$$DAY_NAME; \
+		touch internal/$$YEAR/Day$$DAY_NAME/code.go; \
+		touch internal/$$YEAR/Day$$DAY_NAME/code_test.go; \
+		if [ -n "$$ADVENTOFCODE_SESSION" ]; then \
+			curl -s -H "Cookie: session=$$ADVENTOFCODE_SESSION" \
+				https://adventofcode.com/$$YEAR/day/$$DAY_NUM/input \
+				| perl -pe 'chomp if eof' > internal/data/$$YEAR/Day$$DAY_NAME/input.txt; \
+		else \
+			touch internal/data/$$YEAR/Day$$DAY_NAME/input.txt; \
+		fi; \
+		echo "$$DAY_ARG ready to be solved."; \
+	fi

README.md

@@ -13,38 +13,64 @@ Ultimately, my goal is to complete all the years of Advent of Code here.
 ## Requirements
 
 - Go 1.25
-- Puzzle input
+- Puzzle input (or your session cookie to have it downloaded automatically)
 
 ## Repository Structure
 
 ```
 ├── cmd/
 │   └── aoc/
-│       └── main.go                # CLI entry point that runs solutions
+│       └── main.go               # CLI entry point for running puzzles
 └── internal/
     ├── 2020/
+    │   ├── register.go           # Aggregates import for main.go
     │   ├── DayOne/
-    │   │   ├── code.go            # Go solution for Day 1 (2020)
+    │   │   ├── code.go           # Day 1 solution for 2020
-    │   │   └── code_test.go       # Unit tests for Day 1
+    │   │   └── code_test.go      # Unit tests for Day 1 solution
-    │   └── ...
+    │   └── ...                   # Other days for 2020
     ├── 2021/
-    │   └── ...                    # Additional years and days
+    │   └── ...                   # 2021 days code and tests
     ├── registry/
-    │   └── registry.go            # Central registry for day runners
+    │   └── registry.go           # Central map/registry for finding and running days
     └── data/
         ├── 2020/
         │   ├── DayOne/
-        │   │   └── input.txt      # Puzzle input for Day 1 (2020)
+        │   │   └── input.txt     # Puzzle input for Day 1 (2020)
-        │   └── ...
+        │   └── ...               # Inputs for other days
-        └── ...
+        └── ...                   # Inputs for other years
 ```
 
 Each day's solution is organized into its own folder, named according to the day number (e.g., `DayOne`, `DayTwo`). Inside each folder, you'll find a `code.go` file with the Go implementation of the solution and a `code_test.go` file containing corresponding tests. The input data for each puzzle is located in the `internal/data` directory, mirroring the code structure for easy access.
 
-To connect each solution to the CLI, the repository uses a central registry located in `internal/registry/registry.go`. This registry is essentially a map linking a day key (combining year and day number) to assign a "day runner" which is a struct that specifies the `ParseInput`, `PartOne` and `PartTwo` functions of the day's problem.
+Each year has its own `register.go` file to aggregate imports. To connect each solution to the CLI, the repository uses a central registry located in `internal/registry/registry.go`. This registry is essentially a map linking a day key (combining year and day number) to assign a "day runner" which is a struct that specifies the `ParseInput`, `PartOne` and `PartTwo` functions of the day's problem.
 
 When running a solution, the CLI (`cmd/aoc/main.go`) looks up the appropriate runner from the registry based on your command-line input, uses the parsing function to load the input data, and then runs the desired part (or both parts) using the registered solution functions.
 
+### Starting a new day
+
+```bash
+make 2020D1
+```
+
+If the `ADVENTOFCODE_SESSION` environment variable is set with your Advent of Code session cookie, the input will be downloaded from the AOC website right into the corresponding `internal/data` directory, else it will create an empty `input.txt` file.
+
+Then, it will create the following files:
+
+```bash
+internal/2020/DayOne/code.go
+internal/2020/DayOne/code_test.go
+```
+
+### Handling string answers
+
+Occasionally, a puzzle requires a string as the answer. However, my solution framework expects PartOne/PartTwo functions to return integers.
+
+To work around this, I print the string result (see [2018D2P2](https://git.kharec.info/Kharec/advent-of-code/tree/main/internal/2018/DayTwo/code.go)) and return a dummy integer to satisfy the type requirements.
+
+Meanwhile, the corresponding [test](https://git.kharec.info/Kharec/advent-of-code/tree/main/internal/2018/DayTwo/code_test.go) captures the output and verifies that the correct string is produced.
+
+It's not the most elegant solution, but since only a handful of days across all Advent of Code years require a string result, this compromise keeps the rest of the code simple.
+
 ## Usage
 
 Build the CLI tool:

cmd/aoc/main.go

@@ -1,25 +1,21 @@
 package main
 
 import (
-	"advent-of-code/internal/registry"
 	"fmt"
 	"log"
 	"os"
 	"path/filepath"
 	"regexp"
 
-	_ "advent-of-code/internal/2015/DayOne"
+	"advent-of-code/internal/registry"
-	_ "advent-of-code/internal/2020/DayEight"
+
-	_ "advent-of-code/internal/2020/DayFour"
+	_ "advent-of-code/internal/2015"
-	_ "advent-of-code/internal/2020/DayOne"
+	_ "advent-of-code/internal/2016"
-	_ "advent-of-code/internal/2020/DaySeven"
+	_ "advent-of-code/internal/2018"
-	_ "advent-of-code/internal/2020/DaySix"
+	_ "advent-of-code/internal/2020"
-	_ "advent-of-code/internal/2020/DayThree"
+	_ "advent-of-code/internal/2021"
-	_ "advent-of-code/internal/2020/DayTwo"
+	_ "advent-of-code/internal/2022"
-	_ "advent-of-code/internal/2021/DayOne"
+	_ "advent-of-code/internal/2025"
-	_ "advent-of-code/internal/2021/DayThree"
-	_ "advent-of-code/internal/2021/DayTwo"
-	_ "advent-of-code/internal/2022/DayOne"
 )
 
 func capitalize(day string) string {

internal/2015/DayEight/code.go

@@ -0,0 +1,61 @@
+package dayeight
+
+import (
+	"os"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2015D8", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	result := 0
+	for _, line := range data {
+		codeLength := len(line)
+		memoryLength := 0
+		for idx := 1; idx < len(line)-1; idx++ {
+			if line[idx] == '\\' && idx+1 < len(line)-1 {
+				switch line[idx+1] {
+				case '\\', '"':
+					memoryLength++
+					idx++
+				case 'x':
+					if idx+3 < len(line)-1 {
+						memoryLength++
+						idx += 3
+					}
+				}
+			} else {
+				memoryLength++
+			}
+		}
+		result += codeLength - memoryLength
+	}
+	return result
+}
+
+func PartTwo(data []string) int {
+	result := 0
+	for _, line := range data {
+		originalLength := len(line)
+		encodedLength := 2
+		for _, char := range line {
+			switch char {
+			case '\\', '"':
+				encodedLength += 2
+			default:
+				encodedLength++
+			}
+		}
+		result += encodedLength - originalLength
+	}
+	return result
+}

internal/2015/DayEight/code_test.go

@@ -0,0 +1,26 @@
+package dayeight
+
+import "testing"
+
+var testInput = []string{
+	`""`,
+	`"abc"`,
+	`"aaa\"aaa"`,
+	`"\x27"`,
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 12
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 19
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2015/DayEleven/code.go

@@ -0,0 +1,97 @@
+package dayeleven
+
+import (
+	"os"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2015D11", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) string {
+	content, _ := os.ReadFile(filepath)
+	return string(content)
+}
+
+func findNextValidPassword(data string) string {
+	bytes := []byte(data)
+
+	increment := func() {
+		for idx := len(bytes) - 1; idx >= 0; idx-- {
+			if bytes[idx] == 'z' {
+				bytes[idx] = 'a'
+			} else {
+				bytes[idx]++
+				if bytes[idx] == 'i' || bytes[idx] == 'o' || bytes[idx] == 'l' {
+					bytes[idx]++
+				}
+				for j := idx + 1; j < len(bytes); j++ {
+					bytes[j] = 'a'
+				}
+				return
+			}
+		}
+	}
+
+	increment()
+
+	for {
+		forbiddenPosition := -1
+		for idx := range bytes {
+			if bytes[idx] == 'i' || bytes[idx] == 'o' || bytes[idx] == 'l' {
+				forbiddenPosition = idx
+				break
+			}
+		}
+
+		if forbiddenPosition != -1 {
+			bytes[forbiddenPosition]++
+			if bytes[forbiddenPosition] == 'i' || bytes[forbiddenPosition] == 'o' || bytes[forbiddenPosition] == 'l' {
+				bytes[forbiddenPosition]++
+			}
+			for j := forbiddenPosition + 1; j < len(bytes); j++ {
+				bytes[j] = 'a'
+			}
+			continue
+		}
+
+		hasStraight := false
+		for idx := 0; idx < len(bytes)-2; idx++ {
+			if bytes[idx+1] == bytes[idx]+1 && bytes[idx+2] == bytes[idx]+2 {
+				hasStraight = true
+				break
+			}
+		}
+
+		pairChars := make(map[byte]bool)
+		for idx := 0; idx < len(bytes)-1; idx++ {
+			if bytes[idx] == bytes[idx+1] {
+				pairChars[bytes[idx]] = true
+				idx++
+			}
+		}
+
+		if hasStraight && len(pairChars) >= 2 {
+			break
+		}
+
+		increment()
+	}
+
+	return string(bytes)
+}
+
+func PartOne(data string) int {
+	result := findNextValidPassword(data)
+	println(result)
+	return 0
+}
+
+func PartTwo(data string) int {
+	firstPassword := findNextValidPassword(data)
+	secondPassword := findNextValidPassword(firstPassword)
+	println(secondPassword)
+	return 0
+}

internal/2015/DayFive/code.go

@@ -0,0 +1,77 @@
+package dayfive
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2015D5", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	count := 0
+	for _, line := range data {
+		vowelCount := strings.Count(line, "a") + strings.Count(line, "e") + strings.Count(line, "i") + strings.Count(line, "o") + strings.Count(line, "u")
+		if vowelCount < 3 {
+			continue
+		}
+
+		hasDoubleLetter := false
+		for i := 1; i < len(line); i++ {
+			if line[i] == line[i-1] {
+				hasDoubleLetter = true
+				break
+			}
+		}
+		if !hasDoubleLetter {
+			continue
+		}
+
+		if strings.Contains(line, "ab") || strings.Contains(line, "cd") || strings.Contains(line, "pq") || strings.Contains(line, "xy") {
+			continue
+		}
+
+		count++
+	}
+	return count
+}
+
+func PartTwo(data []string) int {
+	count := 0
+	for _, line := range data {
+		if len(line) < 4 {
+			continue
+		}
+
+		hasNonOverlappingPair := false
+		for i := 0; i < len(line)-1; i++ {
+			pair := line[i : i+2]
+			if strings.Contains(line[i+2:], pair) {
+				hasNonOverlappingPair = true
+				break
+			}
+		}
+		if !hasNonOverlappingPair {
+			continue
+		}
+
+		hasRepeatingLetterWithGap := false
+		for i := 0; i < len(line)-2; i++ {
+			if line[i] == line[i+2] {
+				hasRepeatingLetterWithGap = true
+				break
+			}
+		}
+		if hasRepeatingLetterWithGap {
+			count++
+		}
+	}
+	return count
+}

internal/2015/DayFive/code_test.go

@@ -0,0 +1,32 @@
+package dayfive
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	input := []string{
+		"ugknbfddgicrmopn",
+		"aaa",
+		"jchzalrnumimnmhp",
+		"haegwjzuvuyypxyu",
+		"dvszwmarrgswjxmb",
+	}
+	expected := 2
+	got := PartOne(input)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	input := []string{
+		"qjhvhtzxzqqjkmpb",
+		"xxyxx",
+		"uurcxstgmygtbstg",
+		"ieodomkazucvgmuy",
+	}
+	expected := 2
+	got := PartTwo(input)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2015/DayFour/code.go

@@ -0,0 +1,46 @@
+package dayfour
+
+import (
+	"advent-of-code/internal/registry"
+	"bytes"
+	"crypto/md5"
+	"os"
+	"strconv"
+)
+
+func init() {
+	registry.Register("2015D4", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []byte {
+	content, _ := os.ReadFile(filepath)
+	return bytes.TrimSpace(content)
+}
+
+func findHashWithZeroes(data []byte, zeroes int) int {
+	buffer := make([]byte, len(data), len(data)+10)
+	copy(buffer, data)
+	for idx := 1; ; idx++ {
+		buffer = buffer[:len(data)]
+		buffer = strconv.AppendInt(buffer, int64(idx), 10)
+		hash := md5.Sum(buffer)
+		switch zeroes {
+		case 5:
+			if hash[0] == 0 && hash[1] == 0 && hash[2]&0xF0 == 0 {
+				return idx
+			}
+		case 6:
+			if hash[0] == 0 && hash[1] == 0 && hash[2] == 0 {
+				return idx
+			}
+		}
+	}
+}
+
+func PartOne(data []byte) int {
+	return findHashWithZeroes(data, 5)
+}
+
+func PartTwo(data []byte) int {
+	return findHashWithZeroes(data, 6)
+}

internal/2015/DayFour/code_test.go

@@ -0,0 +1,45 @@
+package dayfour
+
+import (
+	"testing"
+)
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []byte
+		expected int
+	}{
+		{"abcdef", []byte("abcdef"), 609043},
+		{"pqrstuv", []byte("pqrstuv"), 1048970},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []byte
+		expected int
+	}{
+		{"abcdef", []byte("abcdef"), 6742839},
+		{"pqrstuv", []byte("pqrstuv"), 5714438},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartTwo(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartTwo() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}

internal/2015/DayFourteen/code.go

@@ -0,0 +1,108 @@
+package dayfourteen
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var reindeerPattern = regexp.MustCompile(`\w+ can fly (\d+) km/s for (\d+) seconds, but then must rest for (\d+) seconds\.`)
+
+const raceTime = 2503
+
+type Reindeer struct {
+	Speed    int
+	FlyTime  int
+	RestTime int
+	Points   int
+}
+
+func init() {
+	registry.Register("2015D14", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func parseReindeer(line string) Reindeer {
+	matches := reindeerPattern.FindStringSubmatch(line)
+	speed, _ := strconv.Atoi(matches[1])
+	flyTime, _ := strconv.Atoi(matches[2])
+	restTime, _ := strconv.Atoi(matches[3])
+	return Reindeer{Speed: speed, FlyTime: flyTime, RestTime: restTime}
+}
+
+func parseReindeers(data []string) []Reindeer {
+	reindeers := make([]Reindeer, 0, len(data))
+	for _, line := range data {
+		reindeers = append(reindeers, parseReindeer(line))
+	}
+	return reindeers
+}
+
+func (reindeer Reindeer) distanceAtTime(time int) int {
+	cycleTime := reindeer.FlyTime + reindeer.RestTime
+	fullCycles := time / cycleTime
+	distance := fullCycles * reindeer.Speed * reindeer.FlyTime
+	remainingTime := time % cycleTime
+	distance += reindeer.Speed * min(remainingTime, reindeer.FlyTime)
+	return distance
+}
+
+func calculateMaxDistance(data []string, time int) int {
+	reindeers := parseReindeers(data)
+	maxDistance := 0
+
+	for _, reindeer := range reindeers {
+		distance := reindeer.distanceAtTime(time)
+		if distance > maxDistance {
+			maxDistance = distance
+		}
+	}
+
+	return maxDistance
+}
+
+func calculateMaxPoints(data []string, time int) int {
+	reindeers := parseReindeers(data)
+
+	for second := 1; second <= time; second++ {
+		maxDistance := 0
+		distances := make([]int, len(reindeers))
+
+		for idx := range reindeers {
+			distance := reindeers[idx].distanceAtTime(second)
+			distances[idx] = distance
+			if distance > maxDistance {
+				maxDistance = distance
+			}
+		}
+
+		for idx := range reindeers {
+			if distances[idx] == maxDistance {
+				reindeers[idx].Points++
+			}
+		}
+	}
+
+	maxPoints := 0
+	for idx := range reindeers {
+		if reindeers[idx].Points > maxPoints {
+			maxPoints = reindeers[idx].Points
+		}
+	}
+
+	return maxPoints
+}
+
+func PartOne(data []string) int {
+	return calculateMaxDistance(data, raceTime)
+}
+
+func PartTwo(data []string) int {
+	return calculateMaxPoints(data, raceTime)
+}

internal/2015/DayFourteen/code_test.go

@@ -0,0 +1,24 @@
+package dayfourteen
+
+import "testing"
+
+var testInput = []string{
+	"Comet can fly 14 km/s for 10 seconds, but then must rest for 127 seconds.",
+	"Dancer can fly 16 km/s for 11 seconds, but then must rest for 162 seconds.",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 1120
+	got := calculateMaxDistance(testInput, 1000)
+	if got != expected {
+		t.Errorf("calculateMaxDistance(testInput, 1000) = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 689
+	got := calculateMaxPoints(testInput, 1000)
+	if got != expected {
+		t.Errorf("calculateMaxPoints(testInput, 1000) = %d, want %d", got, expected)
+	}
+}

internal/2015/DayNine/code.go

@@ -0,0 +1,106 @@
+package daynine
+
+import (
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2015D9", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func buildDistanceMap(data []string) map[string]map[string]int {
+	distances := make(map[string]map[string]int)
+
+	for _, line := range data {
+		parts := strings.Split(line, " = ")
+		distance, _ := strconv.Atoi(parts[1])
+		route := strings.Split(parts[0], " to ")
+		from, to := route[0], route[1]
+
+		if distances[from] == nil {
+			distances[from] = make(map[string]int)
+		}
+		if distances[to] == nil {
+			distances[to] = make(map[string]int)
+		}
+
+		distances[from][to] = distance
+		distances[to][from] = distance
+	}
+
+	return distances
+}
+
+func getCities(distances map[string]map[string]int) []string {
+	cities := make([]string, 0, len(distances))
+	for city := range distances {
+		cities = append(cities, city)
+	}
+	return cities
+}
+
+func generatePermutations(cities []string) [][]string {
+	if len(cities) == 0 {
+		return [][]string{{}}
+	}
+	var result [][]string
+	for idx, city := range cities {
+		remaining := make([]string, len(cities)-1)
+		copy(remaining[:idx], cities[:idx])
+		copy(remaining[idx:], cities[idx+1:])
+
+		for _, permutations := range generatePermutations(remaining) {
+			result = append(result, append([]string{city}, permutations...))
+		}
+	}
+	return result
+}
+
+func calculateRouteDistance(route []string, distances map[string]map[string]int) int {
+	total := 0
+	for idx := 0; idx < len(route)-1; idx++ {
+		total += distances[route[idx]][route[idx+1]]
+	}
+	return total
+}
+
+func PartOne(data []string) int {
+	distances := buildDistanceMap(data)
+	cities := getCities(distances)
+	permutations := generatePermutations(cities)
+
+	minimalDistance := int(^uint(0) >> 1)
+	for _, route := range permutations {
+		total := calculateRouteDistance(route, distances)
+		if total < minimalDistance {
+			minimalDistance = total
+		}
+	}
+
+	return minimalDistance
+}
+
+func PartTwo(data []string) int {
+	distances := buildDistanceMap(data)
+	cities := getCities(distances)
+	permutations := generatePermutations(cities)
+
+	maximalDistance := 0
+	for _, route := range permutations {
+		total := calculateRouteDistance(route, distances)
+		if total > maximalDistance {
+			maximalDistance = total
+		}
+	}
+
+	return maximalDistance
+}

internal/2015/DayNine/code_test.go

@@ -0,0 +1,25 @@
+package daynine
+
+import "testing"
+
+var testInput = []string{
+	"London to Dublin = 464",
+	"London to Belfast = 518",
+	"Dublin to Belfast = 141",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 605
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 982
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2015/DayOne/code_test.go

@@ -23,7 +23,7 @@ func TestPartOne(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			got := PartOne(tt.input)
 			if got != tt.expected {
-				t.Errorf("PartOne(%q) = %d, want %d", tt.input, got, tt.expected)
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
 			}
 		})
 	}
@@ -43,7 +43,7 @@ func TestPartTwo(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			got := PartTwo(tt.input)
 			if got != tt.expected {
-				t.Errorf("PartTwo(%q) = %d, want %d", tt.input, got, tt.expected)
+				t.Errorf("PartTwo() = %d, want %d", got, tt.expected)
 			}
 		})
 	}

internal/2015/DaySeven/code.go

@@ -0,0 +1,77 @@
+package dayseven
+
+import (
+	"maps"
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2015D7", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) map[string]string {
+	content, _ := os.ReadFile(filepath)
+	instructions := make(map[string]string)
+	for line := range strings.SplitSeq(string(content), "\n") {
+		if parts := strings.Split(line, " -> "); len(parts) == 2 {
+			instructions[parts[1]] = parts[0]
+		}
+	}
+	return instructions
+}
+
+func evaluateWire(wire string, instructions map[string]string) uint16 {
+	cache := make(map[string]uint16)
+	var evaluate func(string) uint16
+	evaluate = func(wire string) uint16 {
+		if value, ok := cache[wire]; ok {
+			return value
+		}
+		if num, err := strconv.Atoi(wire); err == nil {
+			return uint16(num)
+		}
+		expression, exists := instructions[wire]
+		if !exists {
+			return 0
+		}
+		parts := strings.Fields(expression)
+		var result uint16
+		switch {
+		case len(parts) == 1:
+			result = evaluate(parts[0])
+		case parts[0] == "NOT":
+			result = ^evaluate(parts[1])
+		default:
+			left, right := evaluate(parts[0]), evaluate(parts[2])
+			switch parts[1] {
+			case "AND":
+				result = left & right
+			case "OR":
+				result = left | right
+			case "LSHIFT":
+				result = left << right
+			case "RSHIFT":
+				result = left >> right
+			}
+		}
+		cache[wire] = result
+		return result
+	}
+	return evaluate(wire)
+}
+
+func PartOne(data map[string]string) int {
+	return int(evaluateWire("a", data))
+}
+
+func PartTwo(data map[string]string) int {
+	signalA := PartOne(data)
+	instructionsCopy := make(map[string]string, len(data))
+	maps.Copy(instructionsCopy, data)
+	instructionsCopy["b"] = strconv.Itoa(signalA)
+	return int(evaluateWire("a", instructionsCopy))
+}

internal/2015/DaySeven/code_test.go

@@ -0,0 +1,50 @@
+package dayseven
+
+import (
+	"testing"
+)
+
+var testInput = map[string]string{
+	"x": "123",
+	"y": "456",
+	"d": "x AND y",
+	"e": "x OR y",
+	"f": "x LSHIFT 2",
+	"g": "y RSHIFT 2",
+	"h": "NOT x",
+	"i": "NOT y",
+	"a": "d",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 72
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	instructions := map[string]string{
+		"x": "10",
+		"y": "20",
+		"z": "x AND y",
+		"b": "z",
+		"w": "b LSHIFT 1",
+		"v": "NOT b",
+		"u": "w OR v",
+		"a": "u",
+	}
+
+	partOneResult := PartOne(instructions)
+	bValue := uint16(partOneResult)
+	w := bValue << 1
+	v := ^bValue
+	u := w | v
+	expected := int(u)
+
+	got := PartTwo(instructions)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d (PartOne result: %d)", got, expected, partOneResult)
+	}
+}

internal/2015/DaySix/code.go

@@ -0,0 +1,119 @@
+package daysix
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strconv"
+	"strings"
+)
+
+type instruction struct {
+	operation string
+	x1, y1    int
+	x2, y2    int
+}
+
+func init() {
+	registry.Register("2015D6", ParseInput, PartOne, PartTwo)
+}
+
+func parseInstruction(line string) (instruction, bool) {
+	var op string
+	var remaining string
+
+	switch {
+	case strings.HasPrefix(line, "turn on "):
+		op = "on"
+		remaining = strings.TrimPrefix(line, "turn on ")
+	case strings.HasPrefix(line, "turn off "):
+		op = "off"
+		remaining = strings.TrimPrefix(line, "turn off ")
+	case strings.HasPrefix(line, "toggle "):
+		op = "toggle"
+		remaining = strings.TrimPrefix(line, "toggle ")
+	default:
+		return instruction{}, false
+	}
+
+	parts := strings.Split(remaining, " through ")
+	firstCoordinates := strings.Split(parts[0], ",")
+	secondCoordinates := strings.Split(parts[1], ",")
+
+	x1, _ := strconv.Atoi(firstCoordinates[0])
+	y1, _ := strconv.Atoi(firstCoordinates[1])
+	x2, _ := strconv.Atoi(secondCoordinates[0])
+	y2, _ := strconv.Atoi(secondCoordinates[1])
+
+	return instruction{operation: op, x1: x1, y1: y1, x2: x2, y2: y2}, true
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(strings.TrimSpace(string(content)), "\n")
+}
+
+func PartOne(data []string) int {
+	grid := make([]bool, 1000*1000)
+
+	for _, line := range data {
+		instruction, ok := parseInstruction(line)
+		if !ok {
+			continue
+		}
+
+		for y := instruction.y1; y <= instruction.y2; y++ {
+			for x := instruction.x1; x <= instruction.x2; x++ {
+				idx := y*1000 + x
+				switch instruction.operation {
+				case "on":
+					grid[idx] = true
+				case "off":
+					grid[idx] = false
+				case "toggle":
+					grid[idx] = !grid[idx]
+				}
+			}
+		}
+	}
+
+	count := 0
+	for _, lit := range grid {
+		if lit {
+			count++
+		}
+	}
+	return count
+}
+
+func PartTwo(data []string) int {
+	grid := make([]int, 1000*1000)
+
+	for _, line := range data {
+		instruction, ok := parseInstruction(line)
+		if !ok {
+			continue
+		}
+
+		for y := instruction.y1; y <= instruction.y2; y++ {
+			for x := instruction.x1; x <= instruction.x2; x++ {
+				idx := y*1000 + x
+				switch instruction.operation {
+				case "on":
+					grid[idx]++
+				case "off":
+					if grid[idx] > 0 {
+						grid[idx]--
+					}
+				case "toggle":
+					grid[idx] += 2
+				}
+			}
+		}
+	}
+
+	total := 0
+	for _, brightness := range grid {
+		total += brightness
+	}
+	return total
+}

internal/2015/DaySix/code_test.go

@@ -0,0 +1,25 @@
+package daysix
+
+import "testing"
+
+var testInput = []string{
+	"turn on 0,0 through 999,999",
+	"toggle 0,0 through 999,0",
+	"turn off 499,499 through 500,500",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 998996
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 1001996
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2015/DayTen/code.go

@@ -0,0 +1,45 @@
+package dayten
+
+import (
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2015D10", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) string {
+	content, _ := os.ReadFile(filepath)
+	return string(content)
+}
+
+func applyLookAndSay(data string, iterations int) int {
+	for range iterations {
+		var result strings.Builder
+		idx := 0
+		for idx < len(data) {
+			digit := data[idx]
+			count := 1
+			for idx+count < len(data) && data[idx+count] == digit {
+				count++
+			}
+			result.WriteString(strconv.Itoa(count))
+			result.WriteByte(digit)
+			idx += count
+		}
+		data = result.String()
+	}
+	return len(data)
+}
+
+func PartOne(data string) int {
+	return applyLookAndSay(data, 40)
+}
+
+func PartTwo(data string) int {
+	return applyLookAndSay(data, 50)
+}

internal/2015/DayThirteen/code.go

@@ -0,0 +1,141 @@
+package daythirteen
+
+import (
+	"advent-of-code/internal/registry"
+	"math"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var inputPattern = regexp.MustCompile(`(\w+) would (gain|lose) (\d+) happiness units by sitting next to (\w+)\.?`)
+
+func init() {
+	registry.Register("2015D13", ParseInput, PartOne, PartTwo)
+}
+
+func buildHappinessMap(data []string) map[string]map[string]int {
+	happinessMap := make(map[string]map[string]int)
+
+	for _, line := range data {
+		matches := inputPattern.FindStringSubmatch(line)
+		person := matches[1]
+		operation := matches[2]
+		value, _ := strconv.Atoi(matches[3])
+		neighbor := matches[4]
+
+		if happinessMap[person] == nil {
+			happinessMap[person] = make(map[string]int)
+		}
+
+		if operation == "gain" {
+			happinessMap[person][neighbor] = value
+		} else {
+			happinessMap[person][neighbor] = -value
+		}
+	}
+
+	return happinessMap
+}
+
+func getAllPeople(happinessMap map[string]map[string]int) []string {
+	people := make([]string, 0, len(happinessMap))
+	for person := range happinessMap {
+		people = append(people, person)
+	}
+	return people
+}
+
+func generatePermutations(items []string) [][]string {
+	if len(items) == 0 {
+		return [][]string{{}}
+	}
+
+	var result [][]string
+	for idx, item := range items {
+		remaining := make([]string, len(items)-1)
+		copy(remaining[:idx], items[:idx])
+		copy(remaining[idx:], items[idx+1:])
+
+		for _, permutation := range generatePermutations(remaining) {
+			result = append(result, append([]string{item}, permutation...))
+		}
+	}
+	return result
+}
+
+func calculateTotalHappiness(arrangement []string, happinessMap map[string]map[string]int) int {
+	totalHappiness := 0
+	arrangementLength := len(arrangement)
+
+	for idx := range arrangementLength {
+		currentPerson := arrangement[idx]
+		leftNeighbor := arrangement[(idx-1+arrangementLength)%arrangementLength]
+		rightNeighbor := arrangement[(idx+1)%arrangementLength]
+
+		totalHappiness += happinessMap[currentPerson][leftNeighbor]
+		totalHappiness += happinessMap[currentPerson][rightNeighbor]
+	}
+
+	return totalHappiness
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	happinessMap := buildHappinessMap(data)
+	allPeople := getAllPeople(happinessMap)
+
+	fixedPerson := allPeople[0]
+	remainingPeople := allPeople[1:]
+	permutations := generatePermutations(remainingPeople)
+
+	maxHappiness := math.MinInt
+	arrangement := make([]string, len(allPeople))
+	arrangement[0] = fixedPerson
+
+	for _, perm := range permutations {
+		copy(arrangement[1:], perm)
+		totalHappiness := calculateTotalHappiness(arrangement, happinessMap)
+		if totalHappiness > maxHappiness {
+			maxHappiness = totalHappiness
+		}
+	}
+
+	return maxHappiness
+}
+
+func PartTwo(data []string) int {
+	happinessMap := buildHappinessMap(data)
+	allPeople := getAllPeople(happinessMap)
+
+	me := "Me"
+	happinessMap[me] = make(map[string]int)
+	for _, person := range allPeople {
+		happinessMap[person][me] = 0
+		happinessMap[me][person] = 0
+	}
+
+	allPeople = append(allPeople, me)
+	fixedPerson := allPeople[0]
+	remainingPeople := allPeople[1:]
+	permutations := generatePermutations(remainingPeople)
+
+	maxTotalChange := math.MinInt
+	arrangement := make([]string, len(allPeople))
+	arrangement[0] = fixedPerson
+
+	for _, permutation := range permutations {
+		copy(arrangement[1:], permutation)
+		totalHappiness := calculateTotalHappiness(arrangement, happinessMap)
+		if totalHappiness > maxTotalChange {
+			maxTotalChange = totalHappiness
+		}
+	}
+
+	return maxTotalChange
+}

internal/2015/DayThirteen/code_test.go

@@ -0,0 +1,28 @@
+package daythirteen
+
+import "testing"
+
+var testInput = []string{
+	"Alice would gain 54 happiness units by sitting next to Bob",
+	"Alice would lose 79 happiness units by sitting next to Carol",
+	"Alice would lose 2 happiness units by sitting next to David",
+	"Bob would gain 83 happiness units by sitting next to Alice",
+	"Bob would lose 7 happiness units by sitting next to Carol",
+	"Bob would lose 63 happiness units by sitting next to David",
+	"Carol would lose 62 happiness units by sitting next to Alice",
+	"Carol would gain 60 happiness units by sitting next to Bob",
+	"Carol would gain 55 happiness units by sitting next to David",
+	"David would gain 46 happiness units by sitting next to Alice",
+	"David would lose 7 happiness units by sitting next to Bob",
+	"David would gain 41 happiness units by sitting next to Carol",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 330
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+// no test for part two

internal/2015/DayThree/code.go

@@ -0,0 +1,68 @@
+package daythree
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+)
+
+type coordinates struct {
+	x, y int
+}
+
+func init() {
+	registry.Register("2015D3", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) string {
+	content, _ := os.ReadFile(filepath)
+	return string(content)
+}
+
+func PartOne(data string) int {
+	houses := make(map[coordinates]int)
+	x, y := 0, 0
+	houses[coordinates{x, y}] = 1
+	for _, direction := range data {
+		switch direction {
+		case '>':
+			x++
+		case '<':
+			x--
+		case '^':
+			y++
+		case 'v':
+			y--
+		}
+		houses[coordinates{x, y}]++
+	}
+	return len(houses)
+}
+
+func PartTwo(data string) int {
+	houses := make(map[coordinates]int)
+	santaX, santaY := 0, 0
+	robotX, robotY := 0, 0
+	houses[coordinates{0, 0}] = 2
+
+	for idx, direction := range data {
+		var x, y *int
+		if idx%2 == 0 {
+			x, y = &santaX, &santaY
+		} else {
+			x, y = &robotX, &robotY
+		}
+
+		switch direction {
+		case '>':
+			*x++
+		case '<':
+			*x--
+		case '^':
+			*y++
+		case 'v':
+			*y--
+		}
+		houses[coordinates{*x, *y}]++
+	}
+	return len(houses)
+}

internal/2015/DayThree/code_test.go

@@ -0,0 +1,45 @@
+package daythree
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{">", ">", 2},
+		{"^>v<", "^>v<", 4},
+		{"^v^v^v^v^v", "^v^v^v^v^v", 2},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"^v", "^v", 3},
+		{"^>v<", "^>v<", 3},
+		{"^v^v^v^v^v", "^v^v^v^v^v", 11},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartTwo(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartTwo() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}

internal/2015/DayTwelve/code.go

@@ -0,0 +1,68 @@
+package daytwelve
+
+import (
+	"encoding/json"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2015D12", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	re := regexp.MustCompile(`-?\d+`)
+	sum := 0
+	for _, line := range data {
+		matches := re.FindAllString(line, -1)
+		for _, match := range matches {
+			number, _ := strconv.Atoi(match)
+			sum += number
+		}
+	}
+	return sum
+}
+
+func PartTwo(data []string) int {
+	var sumNumbers func(any) int
+	sumNumbers = func(v any) int {
+		switch value := v.(type) {
+		case float64:
+			return int(value)
+		case []any:
+			sum := 0
+			for _, item := range value {
+				sum += sumNumbers(item)
+			}
+			return sum
+		case map[string]any:
+			sum := 0
+			for _, item := range value {
+				if str, ok := item.(string); ok && str == "red" {
+					return 0
+				}
+				sum += sumNumbers(item)
+			}
+			return sum
+		default:
+			return 0
+		}
+	}
+
+	sum := 0
+	for _, line := range data {
+		var value any
+		_ = json.Unmarshal([]byte(line), &value)
+		sum += sumNumbers(value)
+	}
+	return sum
+}

internal/2015/DayTwelve/code_test.go

@@ -0,0 +1,51 @@
+package daytwelve
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"[1,2,3]", "[1,2,3]", 6},
+		{"{\"a\":2,\"b\":4}", "{\"a\":2,\"b\":4}", 6},
+		{"[[[3]]]", "[[[3]]]", 3},
+		{"{\"a\":{\"b\":4},\"c\":-1}", "{\"a\":{\"b\":4},\"c\":-1}", 3},
+		{"{\"a\":[-1,1]}", "{\"a\":[-1,1]}", 0},
+		{"[-1,{\"a\":1}]", "[-1,{\"a\":1}]", 0},
+		{"[]", "[]", 0},
+		{"{}", "{}", 0},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne([]string{tt.input})
+			if got != tt.expected {
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"[1,2,3]", "[1,2,3]", 6},
+		{"[1,{\"c\":\"red\",\"b\":2},3]", "[1,{\"c\":\"red\",\"b\":2},3]", 4},
+		{"{\"d\":\"red\",\"e\":[1,2,3,4],\"f\":5}", "{\"d\":\"red\",\"e\":[1,2,3,4],\"f\":5}", 0},
+		{"[1,\"red\",5]", "[1,\"red\",5]", 6},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartTwo([]string{tt.input})
+			if got != tt.expected {
+				t.Errorf("PartTwo() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}

internal/2015/DayTwo/code.go

@@ -0,0 +1,48 @@
+package daytwo
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2015D2", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	total := 0
+	for _, line := range data {
+		parts := strings.Split(line, "x")
+		length, _ := strconv.Atoi(parts[0])
+		width, _ := strconv.Atoi(parts[1])
+		height, _ := strconv.Atoi(parts[2])
+		total += 2*length*width + 2*width*height + 2*height*length + min(length*width, width*height, height*length)
+	}
+	return total
+}
+
+func PartTwo(data []string) int {
+	total := 0
+	for _, line := range data {
+		parts := strings.Split(line, "x")
+		length, _ := strconv.Atoi(parts[0])
+		width, _ := strconv.Atoi(parts[1])
+		height, _ := strconv.Atoi(parts[2])
+
+		smallest := min(length, width, height)
+		middle := length + width + height - smallest - max(length, width, height)
+
+		perimeter := 2 * (smallest + middle)
+		volume := length * width * height
+
+		total += perimeter + volume
+	}
+	return total
+}

internal/2015/DayTwo/code_test.go

@@ -0,0 +1,43 @@
+package daytwo
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"2x3x4", "2x3x4", 58},
+		{"1x1x10", "1x1x10", 43},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne([]string{tt.input})
+			if got != tt.expected {
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"2x3x4", "2x3x4", 34},
+		{"1x1x10", "1x1x10", 14},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartTwo([]string{tt.input})
+			if got != tt.expected {
+				t.Errorf("PartTwo() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}

internal/2015/register.go

@@ -0,0 +1,18 @@
+package year2015
+
+import (
+	_ "advent-of-code/internal/2015/DayEight"
+	_ "advent-of-code/internal/2015/DayEleven"
+	_ "advent-of-code/internal/2015/DayFive"
+	_ "advent-of-code/internal/2015/DayFour"
+	_ "advent-of-code/internal/2015/DayFourteen"
+	_ "advent-of-code/internal/2015/DayNine"
+	_ "advent-of-code/internal/2015/DayOne"
+	_ "advent-of-code/internal/2015/DaySeven"
+	_ "advent-of-code/internal/2015/DaySix"
+	_ "advent-of-code/internal/2015/DayTen"
+	_ "advent-of-code/internal/2015/DayThirteen"
+	_ "advent-of-code/internal/2015/DayThree"
+	_ "advent-of-code/internal/2015/DayTwelve"
+	_ "advent-of-code/internal/2015/DayTwo"
+)

internal/2016/DayFive/code.go

@@ -0,0 +1,73 @@
+package dayfive
+
+import (
+	"advent-of-code/internal/registry"
+	"crypto/md5"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func init() {
+	registry.Register("2016D5", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) string {
+	content, _ := os.ReadFile(filepath)
+	return string(content)
+}
+
+func PartOne(data string) int {
+	doorIDBytes := []byte(data)
+	doorIDLen := len(doorIDBytes)
+	input := make([]byte, doorIDLen, doorIDLen+20)
+	copy(input, doorIDBytes)
+	password := make([]byte, 0, 8)
+	index := 0
+	hexChars := "0123456789abcdef"
+
+	for len(password) < 8 {
+		indexBytes := strconv.AppendInt(input[:doorIDLen], int64(index), 10)
+		hash := md5.Sum(indexBytes)
+
+		if hash[0] == 0 && hash[1] == 0 && hash[2] < 16 {
+			char := hexChars[hash[2]&0x0F]
+			password = append(password, char)
+		}
+		index++
+	}
+
+	fmt.Println(string(password))
+	return 0
+}
+
+func PartTwo(data string) int {
+	doorIDBytes := []byte(data)
+	doorIDLen := len(doorIDBytes)
+	input := make([]byte, doorIDLen, doorIDLen+20)
+	copy(input, doorIDBytes)
+	password := make([]byte, 8)
+	filled := make([]bool, 8)
+	filledCount := 0
+	index := 0
+	hexChars := "0123456789abcdef"
+
+	for filledCount < 8 {
+		indexBytes := strconv.AppendInt(input[:doorIDLen], int64(index), 10)
+		hash := md5.Sum(indexBytes)
+
+		if hash[0] == 0 && hash[1] == 0 && hash[2] < 16 {
+			position := int(hash[2] & 0x0F)
+			if position < 8 && !filled[position] {
+				char := hexChars[hash[3]>>4]
+				password[position] = char
+				filled[position] = true
+				filledCount++
+			}
+		}
+		index++
+	}
+
+	fmt.Println(string(password))
+	return 0
+}

internal/2016/DayFive/code_test.go

@@ -0,0 +1,58 @@
+package dayfive
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"testing"
+)
+
+var testInput = "abc"
+
+func TestPartOne(t *testing.T) {
+	expected := "18f47a30"
+
+	oldStdout := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("Failed to create pipe: %v", err)
+	}
+	os.Stdout = w
+
+	PartOne(testInput)
+
+	_ = w.Close()
+	os.Stdout = oldStdout
+
+	var buffer bytes.Buffer
+	_, _ = buffer.ReadFrom(r)
+	got := strings.TrimSpace(buffer.String())
+
+	if got != expected {
+		t.Errorf("PartOne() printed %q, want %q", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := "05ace8e3"
+
+	oldStdout := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("Failed to create pipe: %v", err)
+	}
+	os.Stdout = w
+
+	PartTwo(testInput)
+
+	_ = w.Close()
+	os.Stdout = oldStdout
+
+	var buffer bytes.Buffer
+	_, _ = buffer.ReadFrom(r)
+	got := strings.TrimSpace(buffer.String())
+
+	if got != expected {
+		t.Errorf("PartTwo() printed %q, want %q", got, expected)
+	}
+}

internal/2016/DayFour/code.go

@@ -0,0 +1,119 @@
+package dayfour
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2016D4", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func isValidRoom(encryptedName string, expectedChecksum string) bool {
+	letterFrequency := [26]int{}
+
+	for _, character := range encryptedName {
+		if character >= 'a' && character <= 'z' {
+			letterFrequency[character-'a']++
+		}
+	}
+
+	type letterFrequencyPair struct {
+		letter rune
+		count  int
+	}
+
+	letterFrequencyPairs := make([]letterFrequencyPair, 0, 26)
+	for index, frequency := range letterFrequency {
+		if frequency > 0 {
+			letterFrequencyPairs = append(letterFrequencyPairs, letterFrequencyPair{
+				letter: rune('a' + index),
+				count:  frequency,
+			})
+		}
+	}
+
+	sort.Slice(letterFrequencyPairs, func(i, j int) bool {
+		if letterFrequencyPairs[i].count != letterFrequencyPairs[j].count {
+			return letterFrequencyPairs[i].count > letterFrequencyPairs[j].count
+		}
+		return letterFrequencyPairs[i].letter < letterFrequencyPairs[j].letter
+	})
+
+	if len(letterFrequencyPairs) < 5 {
+		return false
+	}
+
+	for index := range 5 {
+		if letterFrequencyPairs[index].letter != rune(expectedChecksum[index]) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func decryptRoomName(encryptedName string, sectorID int) string {
+	result := strings.Builder{}
+	result.Grow(len(encryptedName))
+	shift := sectorID % 26
+	for _, char := range encryptedName {
+		if char == '-' {
+			result.WriteByte(' ')
+		} else if char >= 'a' && char <= 'z' {
+			shifted := ((int(char-'a') + shift) % 26) + 'a'
+			result.WriteByte(byte(shifted))
+		}
+	}
+	return result.String()
+}
+
+var roomPattern = regexp.MustCompile(`^(.+)-(\d+)(?:\[([a-z]{5})\])?$`)
+
+func PartOne(data []string) int {
+	sum := 0
+	for _, line := range data {
+		if line == "" {
+			continue
+		}
+		matches := roomPattern.FindStringSubmatch(line)
+		if len(matches) < 4 || matches[3] == "" {
+			continue
+		}
+		encryptedName := matches[1]
+		sectorIdentifier, _ := strconv.Atoi(matches[2])
+		actualChecksum := matches[3]
+		if isValidRoom(encryptedName, actualChecksum) {
+			sum += sectorIdentifier
+		}
+	}
+	return sum
+}
+
+func PartTwo(data []string) int {
+	for _, line := range data {
+		matches := roomPattern.FindStringSubmatch(line)
+		encryptedName := matches[1]
+		sectorIdentifier, _ := strconv.Atoi(matches[2])
+		checksum := matches[3]
+
+		if !isValidRoom(encryptedName, checksum) {
+			continue
+		}
+
+		decrypted := decryptRoomName(encryptedName, sectorIdentifier)
+		if strings.Contains(decrypted, "northpole") {
+			return sectorIdentifier
+		}
+	}
+	return 0
+}

internal/2016/DayFour/code_test.go

@@ -0,0 +1,29 @@
+package dayfour
+
+import (
+	"testing"
+)
+
+var testInput = []string{
+	"aaaaa-bbb-z-y-x-123[abxyz]",
+	"a-b-c-d-e-f-g-h-987[abcde]",
+	"not-a-real-room-404[oarel]",
+	"totally-real-room-200[decoy]",
+	"ijmockjgz-storage-5[gjoac]",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 1519
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 5
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2016/DayOne/code.go

@@ -0,0 +1,91 @@
+package dayone
+
+import (
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2016D1", ParseInput, PartOne, PartTwo)
+}
+
+type position struct {
+	x, y int
+}
+
+func abs(n int) int {
+	if n < 0 {
+		return -n
+	}
+	return n
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	parts := strings.Split(string(content), ",")
+	for i, p := range parts {
+		parts[i] = strings.TrimSpace(p)
+	}
+	return parts
+}
+
+func PartOne(data []string) int {
+	x, y := 0, 0
+	directions := [][]int{{0, 1}, {1, 0}, {0, -1}, {-1, 0}}
+	currentDirection := 0
+
+	for _, instruction := range data {
+		turn := instruction[0]
+		distance, _ := strconv.Atoi(instruction[1:])
+
+		switch turn {
+		case 'R':
+			currentDirection = (currentDirection + 1) % 4
+		case 'L':
+			currentDirection = (currentDirection + 3) % 4
+		}
+
+		x += directions[currentDirection][0] * distance
+		y += directions[currentDirection][1] * distance
+	}
+
+	return abs(x) + abs(y)
+}
+
+func PartTwo(data []string) int {
+	x, y := 0, 0
+	directions := [][]int{{0, 1}, {1, 0}, {0, -1}, {-1, 0}}
+	currentDirection := 0
+	visited := make(map[position]bool)
+	visited[position{0, 0}] = true
+
+	for _, instruction := range data {
+		turn := instruction[0]
+		distance, _ := strconv.Atoi(instruction[1:])
+
+		switch turn {
+		case 'R':
+			currentDirection = (currentDirection + 1) % 4
+		case 'L':
+			currentDirection = (currentDirection + 3) % 4
+		}
+
+		directionX := directions[currentDirection][0]
+		directionY := directions[currentDirection][1]
+
+		for range distance {
+			x += directionX
+			y += directionY
+			pos := position{x, y}
+			if visited[pos] {
+				return abs(x) + abs(y)
+			}
+			visited[pos] = true
+		}
+	}
+
+	return 0
+}

internal/2016/DayOne/code_test.go

@@ -0,0 +1,47 @@
+package dayone
+
+import (
+	"testing"
+)
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []string
+		expected int
+	}{
+		{
+			name:     "Example 1",
+			input:    []string{"R2", "L3"},
+			expected: 5,
+		},
+		{
+			name:     "Example 2",
+			input:    []string{"R2", "R2", "R2"},
+			expected: 2,
+		},
+		{
+			name:     "Example 3",
+			input:    []string{"R5", "L5", "R5", "R3"},
+			expected: 12,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	input := []string{"R8", "R4", "R4", "R8"}
+	expected := 4
+	got := PartTwo(input)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, 4)
+	}
+}

internal/2016/DayThree/code.go

@@ -0,0 +1,49 @@
+package daythree
+
+import (
+	"advent-of-code/internal/registry"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2016D3", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) [][3]int {
+	content, _ := os.ReadFile(filepath)
+	lines := strings.Split(string(content), "\n")
+	var result [][3]int
+	for _, line := range lines {
+		var a, b, c int
+		fmt.Sscanf(line, "%d %d %d", &a, &b, &c)
+		result = append(result, [3]int{a, b, c})
+
+	}
+	return result
+}
+
+func PartOne(data [][3]int) int {
+	count := 0
+	for _, triangle := range data {
+		a, b, c := triangle[0], triangle[1], triangle[2]
+		if a+b > c && a+c > b && b+c > a {
+			count++
+		}
+	}
+	return count
+}
+
+func PartTwo(data [][3]int) int {
+	count := 0
+	for idx := 0; idx < len(data)-2; idx += 3 {
+		for column := range 3 {
+			a, b, c := data[idx][column], data[idx+1][column], data[idx+2][column]
+			if a+b > c && a+c > b && b+c > a {
+				count++
+			}
+		}
+	}
+	return count
+}

internal/2016/DayThree/code_test.go

@@ -0,0 +1,28 @@
+package daythree
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	input := [][3]int{{5, 10, 25}}
+	expected := 0
+	got := PartOne(input)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	input := [][3]int{
+		{101, 301, 501},
+		{102, 302, 502},
+		{103, 303, 503},
+		{201, 401, 601},
+		{202, 402, 602},
+		{203, 403, 603},
+	}
+	expected := 6
+	got := PartTwo(input)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2016/DayTwo/code.go

@@ -0,0 +1,101 @@
+package daytwo
+
+import (
+	"advent-of-code/internal/registry"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2016D2", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(instructions []string) int {
+	row, column := 1, 1
+
+	keypad := [3][3]int{
+		{1, 2, 3},
+		{4, 5, 6},
+		{7, 8, 9},
+	}
+	code := 0
+
+	for _, line := range instructions {
+		for _, move := range line {
+			switch move {
+			case 'U':
+				if row > 0 {
+					row--
+				}
+			case 'D':
+				if row < 2 {
+					row++
+				}
+			case 'L':
+				if column > 0 {
+					column--
+				}
+			case 'R':
+				if column < 2 {
+					column++
+				}
+			}
+		}
+		code = code*10 + keypad[row][column]
+	}
+
+	return code
+}
+
+func PartTwo(instructions []string) int {
+	row, column := 2, 0
+
+	keypad := [5][5]int{
+		{0, 0, 1, 0, 0},
+		{0, 2, 3, 4, 0},
+		{5, 6, 7, 8, 9},
+		{0, 10, 11, 12, 0},
+		{0, 0, 13, 0, 0},
+	}
+
+	isValidPosition := func(r, c int) bool {
+		return r >= 0 && r < 5 && c >= 0 && c < 5 && keypad[r][c] != 0
+	}
+
+	var codeBuilder strings.Builder
+
+	for _, line := range instructions {
+		for _, move := range line {
+			newRow, newColumn := row, column
+			switch move {
+			case 'U':
+				newRow--
+			case 'D':
+				newRow++
+			case 'L':
+				newColumn--
+			case 'R':
+				newColumn++
+			}
+			if isValidPosition(newRow, newColumn) {
+				row, column = newRow, newColumn
+			}
+		}
+		value := keypad[row][column]
+		if value < 10 {
+			codeBuilder.WriteByte(byte('0' + value))
+		} else {
+			codeBuilder.WriteByte(byte('A' + value - 10))
+		}
+	}
+
+	code := codeBuilder.String()
+	fmt.Println(code)
+	return 0
+}

internal/2016/DayTwo/code_test.go

@@ -0,0 +1,42 @@
+package daytwo
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"testing"
+)
+
+var testInput = []string{"ULL", "RRDDD", "LURDL", "UUUUD"}
+
+func TestPartOne(t *testing.T) {
+	expected := 1985
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := "5DB3"
+
+	oldStdout := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("Failed to create pipe: %v", err)
+	}
+	os.Stdout = w
+
+	PartTwo(testInput)
+
+	_ = w.Close()
+	os.Stdout = oldStdout
+
+	var buffer bytes.Buffer
+	_, _ = buffer.ReadFrom(r)
+	got := strings.TrimSpace(buffer.String())
+
+	if got != expected {
+		t.Errorf("PartTwo() printed %q, want %q", got, expected)
+	}
+}

internal/2016/register.go

@@ -0,0 +1,9 @@
+package year2016
+
+import (
+	_ "advent-of-code/internal/2016/DayFive"
+	_ "advent-of-code/internal/2016/DayFour"
+	_ "advent-of-code/internal/2016/DayOne"
+	_ "advent-of-code/internal/2016/DayThree"
+	_ "advent-of-code/internal/2016/DayTwo"
+)

internal/2018/DayFive/code.go

@@ -0,0 +1,64 @@
+package dayfive
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"unicode"
+)
+
+func init() {
+	registry.Register("2018D5", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) string {
+	content, _ := os.ReadFile(filepath)
+	return string(content)
+}
+
+func reactPolymer(data string) int {
+	stack := []rune{}
+
+	for _, char := range data {
+		if len(stack) == 0 {
+			stack = append(stack, char)
+			continue
+		}
+
+		top := stack[len(stack)-1]
+
+		if unicode.ToLower(top) == unicode.ToLower(char) && top != char {
+			stack = stack[:len(stack)-1]
+		} else {
+			stack = append(stack, char)
+		}
+	}
+
+	return len(stack)
+}
+
+func PartOne(data string) int {
+	return reactPolymer(data)
+}
+
+func PartTwo(data string) int {
+	unitTypes := make(map[rune]bool)
+	for _, char := range data {
+		unitTypes[unicode.ToLower(char)] = true
+	}
+
+	shortestPolymerLength := len(data)
+	for unitType := range unitTypes {
+		filtered := make([]rune, 0, len(data))
+		for _, char := range data {
+			if unicode.ToLower(char) != unitType {
+				filtered = append(filtered, char)
+			}
+		}
+		length := reactPolymer(string(filtered))
+		if length < shortestPolymerLength {
+			shortestPolymerLength = length
+		}
+	}
+
+	return shortestPolymerLength
+}

internal/2018/DayFive/code_test.go

@@ -0,0 +1,21 @@
+package dayfive
+
+import "testing"
+
+var testInput = "dabAcCaCBAcCcaDA"
+
+func TestPartOne(t *testing.T) {
+	expected := 10
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 4
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2018/DayFour/code.go

@@ -0,0 +1,133 @@
+package dayfour
+
+import (
+	"os"
+	"regexp"
+	"slices"
+	"strconv"
+	"strings"
+	"time"
+
+	"advent-of-code/internal/registry"
+)
+
+var (
+	guardRegex = regexp.MustCompile(`Guard #(\d+) begins shift`)
+	timeLayout = "2006-01-02 15:04"
+)
+
+func init() {
+	registry.Register("2018D4", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+type record struct {
+	timestamp time.Time
+	action    string
+	guardID   int
+}
+
+func PartOne(data []string) int {
+	records := make([]record, 0, len(data))
+
+	for _, line := range data {
+		timeStr, action, _ := strings.Cut(line[1:], "] ")
+		timestamp, _ := time.Parse(timeLayout, timeStr)
+		guardID := -1
+		if matches := guardRegex.FindStringSubmatch(action); matches != nil {
+			guardID, _ = strconv.Atoi(matches[1])
+		}
+		records = append(records, record{timestamp, action, guardID})
+	}
+
+	slices.SortFunc(records, func(a, b record) int {
+		return a.timestamp.Compare(b.timestamp)
+	})
+
+	guardSleepMinutes := make(map[int]int)
+	guardMinuteCount := make(map[int]map[int]int)
+	currentGuard := -1
+
+	for i := range records {
+		if records[i].guardID != -1 {
+			currentGuard = records[i].guardID
+			if guardMinuteCount[currentGuard] == nil {
+				guardMinuteCount[currentGuard] = make(map[int]int)
+			}
+		}
+		if records[i].action == "falls asleep" && i+1 < len(records) {
+			start, end := records[i].timestamp.Minute(), records[i+1].timestamp.Minute()
+			guardSleepMinutes[currentGuard] += end - start
+			for m := start; m < end; m++ {
+				guardMinuteCount[currentGuard][m]++
+			}
+		}
+	}
+
+	maxGuard, maxMinutes := -1, 0
+	for id, minutes := range guardSleepMinutes {
+		if minutes > maxMinutes {
+			maxGuard, maxMinutes = id, minutes
+		}
+	}
+
+	maxMinute, maxCount := -1, 0
+	for m, count := range guardMinuteCount[maxGuard] {
+		if count > maxCount {
+			maxMinute, maxCount = m, count
+		}
+	}
+
+	return maxGuard * maxMinute
+}
+
+func PartTwo(data []string) int {
+	records := make([]record, 0, len(data))
+
+	for _, line := range data {
+		timeStr, action, _ := strings.Cut(line[1:], "] ")
+		timestamp, _ := time.Parse(timeLayout, timeStr)
+		guardID := -1
+		if matches := guardRegex.FindStringSubmatch(action); matches != nil {
+			guardID, _ = strconv.Atoi(matches[1])
+		}
+		records = append(records, record{timestamp, action, guardID})
+	}
+
+	slices.SortFunc(records, func(a, b record) int {
+		return a.timestamp.Compare(b.timestamp)
+	})
+
+	guardMinuteCount := make(map[int]map[int]int)
+	currentGuard := -1
+
+	for idx := range records {
+		if records[idx].guardID != -1 {
+			currentGuard = records[idx].guardID
+			if guardMinuteCount[currentGuard] == nil {
+				guardMinuteCount[currentGuard] = make(map[int]int)
+			}
+		}
+		if records[idx].action == "falls asleep" && idx+1 < len(records) {
+			start, end := records[idx].timestamp.Minute(), records[idx+1].timestamp.Minute()
+			for m := start; m < end; m++ {
+				guardMinuteCount[currentGuard][m]++
+			}
+		}
+	}
+
+	maxGuard, maxMinute, maxCount := -1, -1, 0
+	for guardID, minuteCounts := range guardMinuteCount {
+		for minute, count := range minuteCounts {
+			if count > maxCount {
+				maxGuard, maxMinute, maxCount = guardID, minute, count
+			}
+		}
+	}
+
+	return maxGuard * maxMinute
+}

internal/2018/DayFour/code_test.go

@@ -0,0 +1,39 @@
+package dayfour
+
+import "testing"
+
+var testInput = []string{
+	"[1518-11-01 00:00] Guard #10 begins shift",
+	"[1518-11-01 00:05] falls asleep",
+	"[1518-11-01 00:25] wakes up",
+	"[1518-11-01 00:30] falls asleep",
+	"[1518-11-01 00:55] wakes up",
+	"[1518-11-01 23:58] Guard #99 begins shift",
+	"[1518-11-02 00:40] falls asleep",
+	"[1518-11-02 00:50] wakes up",
+	"[1518-11-03 00:05] Guard #10 begins shift",
+	"[1518-11-03 00:24] falls asleep",
+	"[1518-11-03 00:29] wakes up",
+	"[1518-11-04 00:02] Guard #99 begins shift",
+	"[1518-11-04 00:36] falls asleep",
+	"[1518-11-04 00:46] wakes up",
+	"[1518-11-05 00:03] Guard #99 begins shift",
+	"[1518-11-05 00:45] falls asleep",
+	"[1518-11-05 00:55] wakes up",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 240
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 4455
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2018/DayOne/code.go

@@ -0,0 +1,45 @@
+package dayone
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2018D1", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []int {
+	content, _ := os.ReadFile(filepath)
+	var data []int
+	for line := range strings.SplitSeq(string(content), "\n") {
+		num, _ := strconv.Atoi(line)
+		data = append(data, num)
+	}
+	return data
+}
+
+func PartOne(data []int) int {
+	sum := 0
+	for _, num := range data {
+		sum += num
+	}
+	return sum
+}
+
+func PartTwo(data []int) int {
+	seen := make(map[int]bool)
+	sum := 0
+	seen[0] = true
+	for {
+		for _, num := range data {
+			sum += num
+			if seen[sum] {
+				return sum
+			}
+			seen[sum] = true
+		}
+	}
+}

internal/2018/DayOne/code_test.go

@@ -0,0 +1,26 @@
+package dayone
+
+import "testing"
+
+var testInput = []int{
+	+1,
+	-2,
+	3,
+	1,
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 3
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 2
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2018/DayThree/code.go

@@ -0,0 +1,101 @@
+package daythree
+
+import (
+	"advent-of-code/internal/registry"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2018D3", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	coverage := make(map[string]int)
+	re := regexp.MustCompile(`#\d+ @ (\d+),(\d+): (\d+)x(\d+)`)
+
+	for _, line := range data {
+		matches := re.FindStringSubmatch(line)
+
+		left, _ := strconv.Atoi(matches[1])
+		top, _ := strconv.Atoi(matches[2])
+		width, _ := strconv.Atoi(matches[3])
+		height, _ := strconv.Atoi(matches[4])
+
+		for x := left; x < left+width; x++ {
+			for y := top; y < top+height; y++ {
+				key := fmt.Sprintf("%d,%d", x, y)
+				coverage[key]++
+			}
+		}
+	}
+
+	overlapCount := 0
+	for _, count := range coverage {
+		if count >= 2 {
+			overlapCount++
+		}
+	}
+
+	return overlapCount
+}
+
+func PartTwo(data []string) int {
+	coverage := make(map[string]int)
+	re := regexp.MustCompile(`#\d+ @ (\d+),(\d+): (\d+)x(\d+)`)
+
+	for _, line := range data {
+		matches := re.FindStringSubmatch(line)
+
+		left, _ := strconv.Atoi(matches[1])
+		top, _ := strconv.Atoi(matches[2])
+		width, _ := strconv.Atoi(matches[3])
+		height, _ := strconv.Atoi(matches[4])
+
+		for x := left; x < left+width; x++ {
+			for y := top; y < top+height; y++ {
+				key := fmt.Sprintf("%d,%d", x, y)
+				coverage[key]++
+			}
+		}
+	}
+
+	reWithID := regexp.MustCompile(`#(\d+) @ (\d+),(\d+): (\d+)x(\d+)`)
+	for _, line := range data {
+		matches := reWithID.FindStringSubmatch(line)
+		if len(matches) != 6 {
+			continue
+		}
+
+		id, _ := strconv.Atoi(matches[1])
+		left, _ := strconv.Atoi(matches[2])
+		top, _ := strconv.Atoi(matches[3])
+		width, _ := strconv.Atoi(matches[4])
+		height, _ := strconv.Atoi(matches[5])
+
+		overlaps := false
+		for x := left; x < left+width && !overlaps; x++ {
+			for y := top; y < top+height; y++ {
+				key := fmt.Sprintf("%d,%d", x, y)
+				if coverage[key] > 1 {
+					overlaps = true
+					break
+				}
+			}
+		}
+
+		if !overlaps {
+			return id
+		}
+	}
+
+	return 0
+}

internal/2018/DayThree/code_test.go

@@ -0,0 +1,25 @@
+package daythree
+
+import "testing"
+
+var testInput = []string{
+	"#1 @ 1,3: 4x4",
+	"#2 @ 3,1: 4x4",
+	"#3 @ 5,5: 2x2",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 4
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 3
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2018/DayTwo/code.go

@@ -0,0 +1,81 @@
+package daytwo
+
+import (
+	"advent-of-code/internal/registry"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2018D2", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	countWithTwo := 0
+	countWithThree := 0
+
+	for _, boxID := range data {
+		charCounts := make(map[rune]int)
+		for _, char := range boxID {
+			charCounts[char]++
+		}
+
+		hasExactlyTwo := false
+		hasExactlyThree := false
+
+		for _, count := range charCounts {
+			switch count {
+			case 2:
+				hasExactlyTwo = true
+			case 3:
+				hasExactlyThree = true
+			}
+		}
+
+		if hasExactlyTwo {
+			countWithTwo++
+		}
+		if hasExactlyThree {
+			countWithThree++
+		}
+	}
+
+	return countWithTwo * countWithThree
+}
+
+func PartTwo(data []string) int {
+	for idx := range data {
+		for otherIdx := idx + 1; otherIdx < len(data); otherIdx++ {
+			if data[idx] == "" || data[otherIdx] == "" {
+				continue
+			}
+
+			differenceCount := 0
+			differingPosition := -1
+
+			if len(data[idx]) != len(data[otherIdx]) {
+				continue
+			}
+
+			for position := 0; position < len(data[idx]); position++ {
+				if data[idx][position] != data[otherIdx][position] {
+					differenceCount++
+					differingPosition = position
+				}
+			}
+
+			if differenceCount == 1 {
+				common := data[idx][:differingPosition] + data[idx][differingPosition+1:]
+				fmt.Println(common)
+				return 0
+			}
+		}
+	}
+	return 0
+}

internal/2018/DayTwo/code_test.go

@@ -0,0 +1,58 @@
+package daytwo
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestPartOne(t *testing.T) {
+	input := []string{
+		"abcdef",
+		"bababc",
+		"abbcde",
+		"abcccd",
+		"aabcdd",
+		"abcdee",
+		"ababab",
+	}
+	expected := 12
+	got := PartOne(input)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	input := []string{
+		"abcde",
+		"fghij",
+		"klmno",
+		"pqrst",
+		"fguij",
+		"axcye",
+		"wvxyz",
+	}
+	expected := "fgij"
+
+	oldStdout := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("Failed to create pipe: %v", err)
+	}
+	os.Stdout = w
+
+	PartTwo(input)
+
+	_ = w.Close()
+	os.Stdout = oldStdout
+
+	var buffer bytes.Buffer
+	_, _ = buffer.ReadFrom(r)
+	got := strings.TrimSpace(buffer.String())
+
+	if got != expected {
+		t.Errorf("PartTwo() printed %q, want %q", got, expected)
+	}
+}

internal/2018/register.go

@@ -0,0 +1,9 @@
+package year2018
+
+import (
+	_ "advent-of-code/internal/2018/DayFive"
+	_ "advent-of-code/internal/2018/DayFour"
+	_ "advent-of-code/internal/2018/DayOne"
+	_ "advent-of-code/internal/2018/DayThree"
+	_ "advent-of-code/internal/2018/DayTwo"
+)

internal/2020/DayFour/code.go

@@ -91,7 +91,7 @@ func PartTwo(data []string) int {
 			return false
 		}
 		for _, c := range value[1:] {
-			if !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')) {
+			if (c < '0' || c > '9') && (c < 'a' || c > 'f') {
 				return false
 			}
 		}

internal/2020/DayTwo/code.go

@@ -14,11 +14,8 @@ func init() {
 func ParseInput(filepath string) []string {
 	content, _ := os.ReadFile(filepath)
 	lines := strings.Split(string(content), "\n")
-	var data []string
+	data := make([]string, 0, len(lines))
-	for _, line := range lines {
+	return append(data, lines...)
-		data = append(data, line)
-	}
-	return data
 }
 
 func PartOne(data []string) int {

internal/2020/register.go

@@ -0,0 +1,12 @@
+package year2020
+
+import (
+	_ "advent-of-code/internal/2020/DayEight"
+	_ "advent-of-code/internal/2020/DayFive"
+	_ "advent-of-code/internal/2020/DayFour"
+	_ "advent-of-code/internal/2020/DayOne"
+	_ "advent-of-code/internal/2020/DaySeven"
+	_ "advent-of-code/internal/2020/DaySix"
+	_ "advent-of-code/internal/2020/DayThree"
+	_ "advent-of-code/internal/2020/DayTwo"
+)

internal/2021/DayFour/code.go

@@ -0,0 +1,155 @@
+package dayfour
+
+import (
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+const boardSize = 5
+
+func init() {
+	registry.Register("2021D4", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(strings.TrimSpace(string(content)), "\n")
+}
+
+type board struct {
+	numbers      [boardSize][boardSize]int
+	positionMap  map[int][2]int
+	rowCounts    [boardSize]int
+	columnCounts [boardSize]int
+	marked       map[int]bool
+	won          bool
+}
+
+func newBoard() board {
+	return board{
+		positionMap: make(map[int][2]int, boardSize*boardSize),
+		marked:      make(map[int]bool),
+	}
+}
+
+func parseBoards(lines []string) []board {
+	var boards []board
+	current := newBoard()
+	row := 0
+
+	for _, line := range lines {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			if row == boardSize {
+				boards = append(boards, current)
+				current = newBoard()
+				row = 0
+			}
+			continue
+		}
+
+		fields := strings.Fields(line)
+		for column, field := range fields {
+			number, _ := strconv.Atoi(field)
+			current.numbers[row][column] = number
+			current.positionMap[number] = [2]int{row, column}
+		}
+		row++
+	}
+
+	if row == boardSize {
+		boards = append(boards, current)
+	}
+
+	return boards
+}
+
+func (b *board) mark(number int) bool {
+	if b.won {
+		return false
+	}
+
+	position, exists := b.positionMap[number]
+	if !exists {
+		return false
+	}
+
+	b.marked[number] = true
+	row, column := position[0], position[1]
+	b.rowCounts[row]++
+	b.columnCounts[column]++
+
+	if b.rowCounts[row] == boardSize || b.columnCounts[column] == boardSize {
+		b.won = true
+		return true
+	}
+
+	return false
+}
+
+func (b *board) sumUnmarked() int {
+	sum := 0
+	for row := range boardSize {
+		for column := range boardSize {
+			number := b.numbers[row][column]
+			if !b.marked[number] {
+				sum += number
+			}
+		}
+	}
+	return sum
+}
+
+func parseNumbers(line string) []int {
+	numbersStr := strings.Split(line, ",")
+	numbers := make([]int, 0, len(numbersStr))
+	for _, numStr := range numbersStr {
+		num, _ := strconv.Atoi(numStr)
+		numbers = append(numbers, num)
+	}
+	return numbers
+}
+
+func PartOne(data []string) int {
+	numbers := parseNumbers(data[0])
+	boards := parseBoards(data[1:])
+
+	for _, number := range numbers {
+		for idx := range boards {
+			if boards[idx].mark(number) {
+				return boards[idx].sumUnmarked() * number
+			}
+		}
+	}
+
+	return 0
+}
+
+func PartTwo(data []string) int {
+	numbers := parseNumbers(data[0])
+	boards := parseBoards(data[1:])
+
+	wonCount := 0
+	totalBoards := len(boards)
+	var lastWinner *board
+	var lastNumber int
+
+	for _, number := range numbers {
+		for idx := range boards {
+			if boards[idx].mark(number) {
+				wonCount++
+				lastWinner = &boards[idx]
+				lastNumber = number
+
+				if wonCount == totalBoards {
+					return lastWinner.sumUnmarked() * lastNumber
+				}
+			}
+		}
+	}
+
+	return 0
+}

internal/2021/DayFour/code_test.go

@@ -0,0 +1,41 @@
+package dayfour
+
+import "testing"
+
+var testInput = []string{
+	"7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1",
+	"",
+	"22 13 17 11  0",
+	" 8  2 23  4 24",
+	"21  9 14 16  7",
+	" 6 10  3 18  5",
+	" 1 12 20 15 19",
+	"",
+	" 3 15  0  2 22",
+	" 9 18 13 17  5",
+	"19  8  7 25 23",
+	"20 11 10 24  4",
+	"14 21 16 12  6",
+	"",
+	"14 21 17 24  4",
+	"10 16 15  9 19",
+	"18  8 23 26 20",
+	"22 11 13  6  5",
+	" 2  0 12  3  7",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 4512
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 1924
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2021/register.go

@@ -0,0 +1,8 @@
+package year2021
+
+import (
+	_ "advent-of-code/internal/2021/DayFour"
+	_ "advent-of-code/internal/2021/DayOne"
+	_ "advent-of-code/internal/2021/DayThree"
+	_ "advent-of-code/internal/2021/DayTwo"
+)

internal/2022/DayFour/code.go

@@ -0,0 +1,54 @@
+package dayfour
+
+import (
+	"advent-of-code/internal/registry"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2022D4", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	count := 0
+	for _, line := range data {
+		parts := strings.Split(line, ",")
+
+		var firstRangeStart, firstRangeEnd, secondRangeStart, secondRangeEnd int
+		fmt.Sscanf(parts[0], "%d-%d", &firstRangeStart, &firstRangeEnd)
+		fmt.Sscanf(parts[1], "%d-%d", &secondRangeStart, &secondRangeEnd)
+
+		minStart := min(firstRangeStart, secondRangeStart)
+		maxEnd := max(firstRangeEnd, secondRangeEnd)
+
+		if (minStart == firstRangeStart && maxEnd == firstRangeEnd) || (minStart == secondRangeStart && maxEnd == secondRangeEnd) {
+			count++
+		}
+	}
+
+	return count
+}
+
+func PartTwo(data []string) int {
+	count := 0
+	for _, line := range data {
+		parts := strings.Split(line, ",")
+
+		var firstRangeStart, firstRangeEnd, secondRangeStart, secondRangeEnd int
+		fmt.Sscanf(parts[0], "%d-%d", &firstRangeStart, &firstRangeEnd)
+		fmt.Sscanf(parts[1], "%d-%d", &secondRangeStart, &secondRangeEnd)
+
+		if firstRangeStart <= secondRangeEnd && secondRangeStart <= firstRangeEnd {
+			count++
+		}
+	}
+
+	return count
+}

internal/2022/DayFour/code_test.go

@@ -0,0 +1,28 @@
+package dayfour
+
+import "testing"
+
+var testInput = []string{
+	"2-4,6-8",
+	"2-3,4-5",
+	"5-7,7-9",
+	"2-8,3-7",
+	"6-6,4-6",
+	"2-6,4-8",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 2
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 4
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2022/DayThree/code.go

@@ -0,0 +1,87 @@
+package daythree
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2022D3", ParseInput, PartOne, PartTwo)
+}
+
+func buildItemSet(items string) map[rune]bool {
+	itemSet := make(map[rune]bool)
+	for _, item := range items {
+		itemSet[item] = true
+	}
+	return itemSet
+}
+
+func findCommonItem(itemSet map[rune]bool, items string) rune {
+	for _, item := range items {
+		if itemSet[item] {
+			return item
+		}
+	}
+	return 0
+}
+
+func findIntersection(itemSet map[rune]bool, items string) map[rune]bool {
+	intersection := make(map[rune]bool)
+	for _, item := range items {
+		if itemSet[item] {
+			intersection[item] = true
+		}
+	}
+	return intersection
+}
+
+func getItemPriority(item rune) int {
+	if item >= 'a' && item <= 'z' {
+		return int(item - 'a' + 1)
+	}
+	if item >= 'A' && item <= 'Z' {
+		return int(item - 'A' + 27)
+	}
+	return 0
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	totalPriority := 0
+	for _, rucksack := range data {
+		compartmentSize := len(rucksack) / 2
+		firstCompartment := rucksack[:compartmentSize]
+		secondCompartment := rucksack[compartmentSize:]
+
+		firstCompartmentItems := buildItemSet(firstCompartment)
+		commonItem := findCommonItem(firstCompartmentItems, secondCompartment)
+		totalPriority += getItemPriority(commonItem)
+	}
+
+	return totalPriority
+}
+
+func PartTwo(data []string) int {
+	totalPriority := 0
+	for i := 0; i < len(data); i += 3 {
+		if i+2 >= len(data) {
+			break
+		}
+		firstRucksack := data[i]
+		secondRucksack := data[i+1]
+		thirdRucksack := data[i+2]
+
+		firstRucksackItems := buildItemSet(firstRucksack)
+		commonInFirstTwo := findIntersection(firstRucksackItems, secondRucksack)
+		badge := findCommonItem(commonInFirstTwo, thirdRucksack)
+		totalPriority += getItemPriority(badge)
+	}
+
+	return totalPriority
+}

internal/2022/DayThree/code_test.go

@@ -0,0 +1,28 @@
+package daythree
+
+import "testing"
+
+var testInput = []string{
+	"vJrwpWtwJgWrhcsFMMfFFhFp",
+	"jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL",
+	"PmmdzqPrVvPwwTWBwg",
+	"wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn",
+	"ttgJtRGJQctTZtZT",
+	"CrZsJsPPZsGzwwsLwLmpwMDw",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 157
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 70
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2022/DayTwo/code.go

@@ -0,0 +1,62 @@
+package daytwo
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strings"
+)
+
+func init() {
+	registry.Register("2022D2", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(strings.Trim(string(content), "\n"), "\n")
+}
+
+func PartOne(data []string) int {
+	totalScore := 0
+	for _, line := range data {
+		opponent := line[0]
+		me := line[2]
+
+		shapeScore := int(me - 'X' + 1)
+
+		var outcomeScore int
+		if (opponent == 'A' && me == 'Y') || (opponent == 'B' && me == 'Z') || (opponent == 'C' && me == 'X') {
+			outcomeScore = 6
+		} else if (opponent == 'A' && me == 'X') || (opponent == 'B' && me == 'Y') || (opponent == 'C' && me == 'Z') {
+			outcomeScore = 3
+		} else {
+			outcomeScore = 0
+		}
+
+		totalScore += shapeScore + outcomeScore
+	}
+	return totalScore
+}
+
+func PartTwo(data []string) int {
+	totalScore := 0
+	for _, line := range data {
+		opponent := line[0]
+		outcome := line[2]
+
+		var me byte
+		switch outcome {
+		case 'Y':
+			me = 'X' + (opponent - 'A')
+		case 'Z':
+			me = 'X' + ((opponent-'A')+1)%3
+		default:
+			me = 'X' + ((opponent-'A')+2)%3
+		}
+
+		shapeScore := int(me - 'X' + 1)
+		outcomeScore := int(outcome-'X') * 3
+
+		totalScore += shapeScore + outcomeScore
+	}
+	return totalScore
+}

internal/2022/DayTwo/code_test.go

@@ -0,0 +1,25 @@
+package daytwo
+
+import "testing"
+
+var testInput = []string{
+	"A Y",
+	"B X",
+	"C Z",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 15
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 12
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2022/register.go

@@ -0,0 +1,8 @@
+package year2022
+
+import (
+	_ "advent-of-code/internal/2022/DayFour"
+	_ "advent-of-code/internal/2022/DayOne"
+	_ "advent-of-code/internal/2022/DayThree"
+	_ "advent-of-code/internal/2022/DayTwo"
+)

internal/2025/DayEight/code.go

@@ -0,0 +1,210 @@
+package dayeight
+
+import (
+	"cmp"
+	"container/heap"
+	"os"
+	"slices"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2025D8", ParseInput, PartOne, PartTwo)
+}
+
+type JunctionBox struct {
+	X, Y, Z int
+}
+
+type UnionFind struct {
+	parent []int
+	size   []int
+}
+
+type Connection struct {
+	firstJunctionBox, secondJunctionBox int
+	squaredDistance                     int
+}
+
+type ConnectionHeap []Connection
+
+func (h ConnectionHeap) Len() int           { return len(h) }
+func (h ConnectionHeap) Less(i, j int) bool { return h[i].squaredDistance > h[j].squaredDistance }
+func (h ConnectionHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
+func (h *ConnectionHeap) Push(x any)        { *h = append(*h, x.(Connection)) }
+func (h *ConnectionHeap) Pop() any {
+	old := *h
+	n := len(old)
+	x := old[n-1]
+	*h = old[0 : n-1]
+	return x
+}
+
+func NewUnionFind(count int) *UnionFind {
+	parent := make([]int, count)
+	size := make([]int, count)
+	for idx := range parent {
+		parent[idx] = idx
+		size[idx] = 1
+	}
+	return &UnionFind{parent: parent, size: size}
+}
+
+func (uf *UnionFind) Find(junctionBox int) int {
+	if uf.parent[junctionBox] != junctionBox {
+		uf.parent[junctionBox] = uf.Find(uf.parent[junctionBox])
+	}
+	return uf.parent[junctionBox]
+}
+
+func (uf *UnionFind) Union(junctionBox1, junctionBox2 int) (bool, int) {
+	root1 := uf.Find(junctionBox1)
+	root2 := uf.Find(junctionBox2)
+	if root1 == root2 {
+		return false, root1
+	}
+	if uf.size[root1] < uf.size[root2] {
+		root1, root2 = root2, root1
+	}
+	uf.parent[root2] = root1
+	uf.size[root1] += uf.size[root2]
+	return true, root1
+}
+
+func parseJunctionBoxes(data []string) []JunctionBox {
+	var junctionBoxes []JunctionBox
+	for _, line := range data {
+		parts := strings.Split(line, ",")
+		x, _ := strconv.Atoi(parts[0])
+		y, _ := strconv.Atoi(parts[1])
+		z, _ := strconv.Atoi(parts[2])
+		junctionBoxes = append(junctionBoxes, JunctionBox{X: x, Y: y, Z: z})
+	}
+	return junctionBoxes
+}
+
+func generateAllConnections(junctionBoxes []JunctionBox) []Connection {
+	junctionBoxCount := len(junctionBoxes)
+	connections := make([]Connection, 0, junctionBoxCount*(junctionBoxCount-1)/2)
+
+	for i := range junctionBoxCount {
+		for j := i + 1; j < junctionBoxCount; j++ {
+			dx := junctionBoxes[i].X - junctionBoxes[j].X
+			dy := junctionBoxes[i].Y - junctionBoxes[j].Y
+			dz := junctionBoxes[i].Z - junctionBoxes[j].Z
+			squaredDistance := dx*dx + dy*dy + dz*dz
+
+			connections = append(connections, Connection{
+				firstJunctionBox:  i,
+				secondJunctionBox: j,
+				squaredDistance:   squaredDistance,
+			})
+		}
+	}
+
+	slices.SortFunc(connections, func(a, b Connection) int {
+		return cmp.Compare(a.squaredDistance, b.squaredDistance)
+	})
+
+	return connections
+}
+
+func findKSmallestConnections(junctionBoxes []JunctionBox, k int) []Connection {
+	junctionBoxCount := len(junctionBoxes)
+	connectionHeap := make(ConnectionHeap, 0, k)
+	heap.Init(&connectionHeap)
+
+	for i := range junctionBoxCount {
+		for j := i + 1; j < junctionBoxCount; j++ {
+			dx := junctionBoxes[i].X - junctionBoxes[j].X
+			dy := junctionBoxes[i].Y - junctionBoxes[j].Y
+			dz := junctionBoxes[i].Z - junctionBoxes[j].Z
+			squaredDistance := dx*dx + dy*dy + dz*dz
+
+			connection := Connection{
+				firstJunctionBox:  i,
+				secondJunctionBox: j,
+				squaredDistance:   squaredDistance,
+			}
+
+			if len(connectionHeap) < k {
+				heap.Push(&connectionHeap, connection)
+			} else if connection.squaredDistance < connectionHeap[0].squaredDistance {
+				heap.Pop(&connectionHeap)
+				heap.Push(&connectionHeap, connection)
+			}
+		}
+	}
+
+	connections := make([]Connection, 0, len(connectionHeap))
+	for connectionHeap.Len() > 0 {
+		connections = append(connections, heap.Pop(&connectionHeap).(Connection))
+	}
+
+	slices.SortFunc(connections, func(a, b Connection) int {
+		return cmp.Compare(a.squaredDistance, b.squaredDistance)
+	})
+
+	return connections
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	junctionBoxes := parseJunctionBoxes(data)
+	junctionBoxCount := len(junctionBoxes)
+
+	targetPairs := 1000
+	if junctionBoxCount <= 20 {
+		targetPairs = 10
+	}
+
+	connections := findKSmallestConnections(junctionBoxes, targetPairs)
+
+	uf := NewUnionFind(junctionBoxCount)
+	for _, connection := range connections {
+		uf.Union(connection.firstJunctionBox, connection.secondJunctionBox)
+	}
+
+	circuitSizes := make(map[int]int)
+	for idx := range junctionBoxes {
+		root := uf.Find(idx)
+		circuitSizes[root] = uf.size[root]
+	}
+
+	sizes := make([]int, 0, len(circuitSizes))
+	for _, size := range circuitSizes {
+		sizes = append(sizes, size)
+	}
+
+	slices.Sort(sizes)
+	slices.Reverse(sizes)
+
+	return sizes[0] * sizes[1] * sizes[2]
+}
+
+func PartTwo(data []string) int {
+	junctionBoxes := parseJunctionBoxes(data)
+	connections := generateAllConnections(junctionBoxes)
+
+	uf := NewUnionFind(len(junctionBoxes))
+	var lastConnection Connection
+
+	for _, connection := range connections {
+		merged, root := uf.Union(connection.firstJunctionBox, connection.secondJunctionBox)
+		if merged {
+			lastConnection = connection
+			if uf.size[root] == len(junctionBoxes) {
+				break
+			}
+		}
+	}
+
+	return junctionBoxes[lastConnection.firstJunctionBox].X * junctionBoxes[lastConnection.secondJunctionBox].X
+}

internal/2025/DayEight/code_test.go

@@ -0,0 +1,42 @@
+package dayeight
+
+import "testing"
+
+var testInput = []string{
+	"162,817,812",
+	"57,618,57",
+	"906,360,560",
+	"592,479,940",
+	"352,342,300",
+	"466,668,158",
+	"542,29,236",
+	"431,825,988",
+	"739,650,466",
+	"52,470,668",
+	"216,146,977",
+	"819,987,18",
+	"117,168,530",
+	"805,96,715",
+	"346,949,466",
+	"970,615,88",
+	"941,993,340",
+	"862,61,35",
+	"984,92,344",
+	"425,690,689",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 40
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 25272
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DayFive/code.go

@@ -0,0 +1,125 @@
+package dayfive
+
+import (
+	"os"
+	"slices"
+	"sort"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+type freshRange struct {
+	start int
+	end   int
+}
+
+func init() {
+	registry.Register("2025D5", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	var freshRanges []freshRange
+	var ingredientIDs []int
+	separatorFound := false
+
+	for _, line := range data {
+		if line == "" {
+			separatorFound = true
+			continue
+		}
+
+		if !separatorFound {
+			startStr, endStr, _ := strings.Cut(line, "-")
+			start, _ := strconv.Atoi(startStr)
+			end, _ := strconv.Atoi(endStr)
+			freshRanges = append(freshRanges, freshRange{start: start, end: end})
+		} else {
+			id, _ := strconv.Atoi(line)
+			ingredientIDs = append(ingredientIDs, id)
+		}
+	}
+
+	slices.SortFunc(freshRanges, func(a, b freshRange) int {
+		switch {
+		case a.start < b.start:
+			return -1
+		case a.start > b.start:
+			return 1
+		default:
+			return 0
+		}
+	})
+
+	freshCount := 0
+	for _, id := range ingredientIDs {
+		idx := sort.Search(len(freshRanges), func(idx int) bool {
+			return freshRanges[idx].start > id
+		})
+
+		for i := idx - 1; i >= 0 && freshRanges[i].start <= id; i-- {
+			if id <= freshRanges[i].end {
+				freshCount++
+				break
+			}
+		}
+	}
+
+	return freshCount
+}
+
+func PartTwo(data []string) int {
+	var freshRanges []freshRange
+
+	for _, line := range data {
+		if line == "" {
+			break
+		}
+
+		startStr, endStr, _ := strings.Cut(line, "-")
+		start, _ := strconv.Atoi(startStr)
+		end, _ := strconv.Atoi(endStr)
+		freshRanges = append(freshRanges, freshRange{start: start, end: end})
+	}
+
+	slices.SortFunc(freshRanges, func(a, b freshRange) int {
+		switch {
+		case a.start < b.start:
+			return -1
+		case a.start > b.start:
+			return 1
+		default:
+			return 0
+		}
+	})
+
+	var mergedRanges []freshRange
+	for _, r := range freshRanges {
+		if len(mergedRanges) == 0 {
+			mergedRanges = append(mergedRanges, r)
+			continue
+		}
+
+		lastRange := &mergedRanges[len(mergedRanges)-1]
+		if r.start <= lastRange.end+1 {
+			if r.end > lastRange.end {
+				lastRange.end = r.end
+			}
+		} else {
+			mergedRanges = append(mergedRanges, r)
+		}
+	}
+
+	totalFreshIDs := 0
+	for _, r := range mergedRanges {
+		totalFreshIDs += r.end - r.start + 1
+	}
+
+	return totalFreshIDs
+}

internal/2025/DayFive/code_test.go

@@ -0,0 +1,33 @@
+package dayfive
+
+import "testing"
+
+var testInput = []string{
+	"3-5",
+	"10-14",
+	"16-20",
+	"12-18",
+	"",
+	"1",
+	"5",
+	"8",
+	"11",
+	"17",
+	"32",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 3
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 14
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DayFour/code.go

@@ -0,0 +1,104 @@
+package dayfour
+
+import (
+	"os"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+type position struct {
+	row, column int
+}
+
+var directions = []position{
+	{-1, -1},
+	{-1, 0},
+	{-1, 1},
+	{0, -1},
+	{0, 1},
+	{1, -1},
+	{1, 0},
+	{1, 1},
+}
+
+func init() {
+	registry.Register("2025D4", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	isRoll := make(map[position]bool)
+
+	for row := range data {
+		for column := 0; column < len(data[row]); column++ {
+			if data[row][column] == '@' {
+				isRoll[position{row, column}] = true
+			}
+		}
+	}
+
+	accessibleRolls := 0
+	for pos := range isRoll {
+		adjacentRolls := 0
+		for _, direction := range directions {
+			neighbor := position{pos.row + direction.row, pos.column + direction.column}
+			if isRoll[neighbor] {
+				adjacentRolls++
+			}
+		}
+
+		if adjacentRolls < 4 {
+			accessibleRolls++
+		}
+	}
+
+	return accessibleRolls
+}
+
+func PartTwo(data []string) int {
+	isRoll := make(map[position]bool)
+
+	for row := range data {
+		for column := 0; column < len(data[row]); column++ {
+			if data[row][column] == '@' {
+				isRoll[position{row, column}] = true
+			}
+		}
+	}
+
+	totalRemoved := 0
+
+	for {
+		accessibleRolls := make(map[position]bool)
+
+		for pos := range isRoll {
+			adjacentRolls := 0
+			for _, direction := range directions {
+				neighbor := position{pos.row + direction.row, pos.column + direction.column}
+				if isRoll[neighbor] {
+					adjacentRolls++
+				}
+			}
+
+			if adjacentRolls < 4 {
+				accessibleRolls[pos] = true
+			}
+		}
+
+		if len(accessibleRolls) == 0 {
+			break
+		}
+
+		for pos := range accessibleRolls {
+			delete(isRoll, pos)
+			totalRemoved++
+		}
+	}
+
+	return totalRemoved
+}

internal/2025/DayFour/code_test.go

@@ -0,0 +1,32 @@
+package dayfour
+
+import "testing"
+
+var testInput = []string{
+	"..@@.@@@@.",
+	"@@@.@.@.@@",
+	"@@@@@.@.@@",
+	"@.@@@@..@.",
+	"@@.@@@@.@@",
+	".@@@@@@@.@",
+	".@.@.@.@@@",
+	"@.@@@.@@@@",
+	".@@@@@@@@.",
+	"@.@.@@@.@.",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 13
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 43
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DayNine/code.go

@@ -0,0 +1,234 @@
+package daynine
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2025D9", ParseInput, PartOne, PartTwo)
+}
+
+type Point struct {
+	x, y int
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func parsePoints(data []string) []Point {
+	points := make([]Point, 0, len(data))
+	for _, line := range data {
+		parts := strings.Split(line, ",")
+		x, _ := strconv.Atoi(parts[0])
+		y, _ := strconv.Atoi(parts[1])
+		points = append(points, Point{x: x, y: y})
+	}
+	return points
+}
+
+func abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func minMax(a, b int) (int, int) {
+	if a > b {
+		return b, a
+	}
+	return a, b
+}
+
+func compressCoordinates(points []Point) ([]int, []int, map[int]int, map[int]int) {
+	xs := make(map[int]bool)
+	ys := make(map[int]bool)
+	for _, point := range points {
+		xs[point.x] = true
+		ys[point.y] = true
+	}
+	sortedX := make([]int, 0, len(xs))
+	sortedY := make([]int, 0, len(ys))
+	for x := range xs {
+		sortedX = append(sortedX, x)
+	}
+	for y := range ys {
+		sortedY = append(sortedY, y)
+	}
+	slices.Sort(sortedX)
+	slices.Sort(sortedY)
+
+	mapX := make(map[int]int, len(sortedX))
+	mapY := make(map[int]int, len(sortedY))
+	for idx, x := range sortedX {
+		mapX[x] = 2 * idx
+	}
+	for idx, y := range sortedY {
+		mapY[y] = 2 * idx
+	}
+	return sortedX, sortedY, mapX, mapY
+}
+
+func drawBoundary(grid [][]bool, points []Point, mapX, mapY map[int]int) {
+	for idx := range points {
+		current, next := points[idx], points[(idx+1)%len(points)]
+		cx1, cy1 := mapX[current.x], mapY[current.y]
+		cx2, cy2 := mapX[next.x], mapY[next.y]
+
+		if cx1 == cx2 {
+			minY, maxY := minMax(cy1, cy2)
+			for y := minY; y <= maxY; y++ {
+				grid[cx1][y] = true
+			}
+		} else {
+			minX, maxX := minMax(cx1, cx2)
+			for x := minX; x <= maxX; x++ {
+				grid[x][cy1] = true
+			}
+		}
+	}
+}
+
+func scanLineFill(grid [][]bool, points []Point, mapX, mapY map[int]int, _, height int) {
+	type edge struct {
+		x, yMin, yMax int
+	}
+	edges := make([]edge, 0, len(points))
+	for idx := range points {
+		current, next := points[idx], points[(idx+1)%len(points)]
+		if current.x == next.x {
+			minY, maxY := minMax(mapY[current.y], mapY[next.y])
+			edges = append(edges, edge{mapX[current.x], minY, maxY})
+		}
+	}
+
+	for y := range height {
+		crossings := make([]int, 0, len(edges))
+		for _, e := range edges {
+			if e.yMin <= y && y < e.yMax {
+				crossings = append(crossings, e.x)
+			}
+		}
+		slices.Sort(crossings)
+		for i := 0; i < len(crossings)-1; i += 2 {
+			for x := crossings[i]; x <= crossings[i+1]; x++ {
+				grid[x][y] = true
+			}
+		}
+	}
+}
+
+func forceEmptyGaps(grid [][]bool, sortedX, sortedY []int, width, height int) {
+	for idx := 0; idx < len(sortedX)-1; idx++ {
+		if sortedX[idx+1] == sortedX[idx]+1 {
+			cx := 2*idx + 1
+			for y := range height {
+				grid[cx][y] = true
+			}
+		}
+	}
+	for idx := 0; idx < len(sortedY)-1; idx++ {
+		if sortedY[idx+1] == sortedY[idx]+1 {
+			cy := 2*idx + 1
+			for x := range width {
+				grid[x][cy] = true
+			}
+		}
+	}
+}
+
+func buildPrefixSum(grid [][]bool, width, height int) [][]int {
+	sum := make([][]int, width+1)
+	for idx := range sum {
+		sum[idx] = make([]int, height+1)
+	}
+	for i := range width {
+		for j := range height {
+			value := 0
+			if grid[i][j] {
+				value = 1
+			}
+			sum[i+1][j+1] = value + sum[i][j+1] + sum[i+1][j] - sum[i][j]
+		}
+	}
+	return sum
+}
+
+func getSum(sum [][]int, x1, y1, x2, y2 int) int {
+	return sum[x2+1][y2+1] - sum[x1][y2+1] - sum[x2+1][y1] + sum[x1][y1]
+}
+
+func PartOne(data []string) int {
+	points := parsePoints(data)
+	maxArea := 0
+
+	for i := range points {
+		for j := i + 1; j < len(points); j++ {
+			dx := abs(points[i].x - points[j].x)
+			dy := abs(points[i].y - points[j].y)
+
+			if area := (dx + 1) * (dy + 1); area > maxArea {
+				maxArea = area
+			}
+		}
+	}
+	return maxArea
+}
+
+func PartTwo(data []string) int {
+	points := parsePoints(data)
+	sortedX, sortedY, mapX, mapY := compressCoordinates(points)
+
+	width, height := 2*len(sortedX), 2*len(sortedY)
+	grid := make([][]bool, width)
+	for idx := range grid {
+		grid[idx] = make([]bool, height)
+	}
+
+	drawBoundary(grid, points, mapX, mapY)
+	scanLineFill(grid, points, mapX, mapY, width, height)
+	forceEmptyGaps(grid, sortedX, sortedY, width, height)
+
+	sum := buildPrefixSum(grid, width, height)
+
+	compressedPoints := make([]Point, len(points))
+	for idx, point := range points {
+		compressedPoints[idx] = Point{mapX[point.x], mapY[point.y]}
+	}
+
+	maxArea := 0
+	for i := range points {
+		for j := i + 1; j < len(points); j++ {
+			p1, p2 := points[i], points[j]
+			dx := abs(p1.x - p2.x)
+			dy := abs(p1.y - p2.y)
+
+			if dx == 0 || dy == 0 {
+				continue
+			}
+
+			area := (dx + 1) * (dy + 1)
+			if area <= maxArea {
+				continue
+			}
+
+			cx1, cy1 := compressedPoints[i].x, compressedPoints[i].y
+			cx2, cy2 := compressedPoints[j].x, compressedPoints[j].y
+			minCX, maxCX := minMax(cx1, cx2)
+			minCY, maxCY := minMax(cy1, cy2)
+
+			totalCells := (maxCX - minCX + 1) * (maxCY - minCY + 1)
+			if getSum(sum, minCX, minCY, maxCX, maxCY) == totalCells {
+				maxArea = area
+			}
+		}
+	}
+
+	return maxArea
+}

internal/2025/DayNine/code_test.go

@@ -0,0 +1,30 @@
+package daynine
+
+import "testing"
+
+var testInput = []string{
+	"7,1",
+	"11,1",
+	"11,7",
+	"9,7",
+	"9,5",
+	"2,5",
+	"2,3",
+	"7,3",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 50
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 24
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DayOne/code.go

@@ -0,0 +1,63 @@
+package dayone
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2025D1", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	position := 50
+	count := 0
+
+	for _, rotation := range data {
+		direction := rotation[0]
+		distance, _ := strconv.Atoi(rotation[1:])
+
+		if direction == 'L' {
+			position = (position - distance + 100) % 100
+		} else {
+			position = (position + distance) % 100
+		}
+
+		if position == 0 {
+			count++
+		}
+	}
+
+	return count
+}
+
+func PartTwo(data []string) int {
+	position := 50
+	count := 0
+
+	for _, rotation := range data {
+		direction := rotation[0]
+		distance, _ := strconv.Atoi(rotation[1:])
+
+		for range distance {
+			if direction == 'L' {
+				position = (position - 1 + 100) % 100
+			} else {
+				position = (position + 1) % 100
+			}
+
+			if position == 0 {
+				count++
+			}
+		}
+	}
+
+	return count
+}

internal/2025/DayOne/code_test.go

@@ -0,0 +1,32 @@
+package dayone
+
+import "testing"
+
+var testInput = []string{
+	"L68",
+	"L30",
+	"R48",
+	"L5",
+	"R60",
+	"L55",
+	"L1",
+	"L99",
+	"R14",
+	"L82",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 3
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 6
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DaySeven/code.go

@@ -0,0 +1,106 @@
+package dayseven
+
+import (
+	"os"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2025D7", ParseInput, PartOne, PartTwo)
+}
+
+type Position struct {
+	row    int
+	column int
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func findStart(data []string) (int, int) {
+	for row := range data {
+		if column := strings.IndexByte(data[row], 'S'); column != -1 {
+			return row, column
+		}
+	}
+	return -1, -1
+}
+
+func PartOne(data []string) int {
+	rows, columns := len(data), len(data[0])
+	startRow, startColumn := findStart(data)
+
+	queue := []Position{{startRow, startColumn}}
+	activated := make(map[Position]bool)
+	splits := 0
+
+	for len(queue) > 0 {
+		current := queue[0]
+		queue = queue[1:]
+
+		row := current.row + 1
+		column := current.column
+
+		for row < rows && data[row][column] != '^' {
+			row++
+		}
+
+		if row < rows {
+			splitPosition := Position{row, column}
+			if !activated[splitPosition] {
+				activated[splitPosition] = true
+				splits++
+
+				if column > 0 {
+					queue = append(queue, Position{row, column - 1})
+				}
+				if column < columns-1 {
+					queue = append(queue, Position{row, column + 1})
+				}
+			}
+		}
+	}
+
+	return splits
+}
+
+func PartTwo(input []string) int {
+	rows, columns := len(input), len(input[0])
+	startRow, startColumn := findStart(input)
+
+	cache := make(map[Position]int)
+
+	var countTimelines func(row, column int) int
+	countTimelines = func(row, column int) int {
+		position := Position{row, column}
+		if count, exists := cache[position]; exists {
+			return count
+		}
+
+		r, c := row+1, column
+		for r < rows && input[r][c] != '^' {
+			r++
+		}
+
+		if r == rows {
+			return 1
+		}
+
+		total := 0
+		if c > 0 {
+			total += countTimelines(r, c-1)
+		}
+		if c < columns-1 {
+			total += countTimelines(r, c+1)
+		}
+
+		cache[position] = total
+		return total
+	}
+
+	return countTimelines(startRow, startColumn)
+}

internal/2025/DaySeven/code_test.go

@@ -0,0 +1,38 @@
+package dayseven
+
+import "testing"
+
+var testInput = []string{
+	".......S.......",
+	"...............",
+	".......^.......",
+	"...............",
+	"......^.^......",
+	"...............",
+	".....^.^.^.....",
+	"...............",
+	"....^.^...^....",
+	"...............",
+	"...^.^...^.^...",
+	"...............",
+	"..^...^.....^..",
+	"...............",
+	".^.^.^.^.^...^.",
+	"...............",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 21
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 40
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DaySix/code.go

@@ -0,0 +1,174 @@
+package daysix
+
+import (
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2025D6", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(strings.TrimRight(string(content), "\n"), "\n")
+}
+
+func transpose(lines []string) []string {
+	maxWidth := 0
+	for _, line := range lines {
+		if len(line) > maxWidth {
+			maxWidth = len(line)
+		}
+	}
+
+	transposed := make([]string, maxWidth)
+	for column := 0; column < maxWidth; column++ {
+		var builder strings.Builder
+		for _, line := range lines {
+			if column < len(line) {
+				builder.WriteByte(line[column])
+			} else {
+				builder.WriteByte(' ')
+			}
+		}
+		transposed[column] = builder.String()
+	}
+
+	return transposed
+}
+
+func isSpaceColumn(column string) bool {
+	return strings.TrimSpace(column) == ""
+}
+
+func extractRowFromColumns(transposed []string, row, startColumn, endColumn int) string {
+	var builder strings.Builder
+	for column := startColumn; column <= endColumn && column < len(transposed); column++ {
+		if row < len(transposed[column]) {
+			builder.WriteByte(transposed[column][row])
+		} else {
+			builder.WriteByte(' ')
+		}
+	}
+	return builder.String()
+}
+
+func extractNumbers(transposed []string, startColumn, endColumn, operationRow int) []int {
+	numbers := make([]int, 0)
+	for row := range operationRow {
+		rowStr := extractRowFromColumns(transposed, row, startColumn, endColumn)
+		trimmed := strings.TrimSpace(rowStr)
+		fields := strings.FieldsSeq(trimmed)
+		for field := range fields {
+			if number, err := strconv.Atoi(field); err == nil {
+				numbers = append(numbers, number)
+			}
+		}
+	}
+	return numbers
+}
+
+func extractNumberFromColumn(column string, operationRow int) (int, bool) {
+	numberStr := strings.Map(func(r rune) rune {
+		if r >= '0' && r <= '9' {
+			return r
+		}
+		return -1
+	}, column[:min(operationRow, len(column))])
+	number, _ := strconv.Atoi(numberStr)
+	return number, true
+}
+
+func extractOperation(segment string) byte {
+	if idx := strings.IndexAny(segment, "+*"); idx != -1 {
+		return segment[idx]
+	}
+	return 0
+}
+
+func applyOperation(numbers []int, operation byte) int {
+	result := numbers[0]
+	if operation == '+' {
+		for idx := 1; idx < len(numbers); idx++ {
+			result += numbers[idx]
+		}
+	} else {
+		for idx := 1; idx < len(numbers); idx++ {
+			result *= numbers[idx]
+		}
+	}
+	return result
+}
+
+func PartOne(data []string) int {
+	operationRow := len(data) - 1
+	transposed := transpose(data)
+
+	total := 0
+	column := 0
+	for column < len(transposed) {
+		if isSpaceColumn(transposed[column]) {
+			column++
+			continue
+		}
+
+		startColumn := column
+		for column < len(transposed) && !isSpaceColumn(transposed[column]) {
+			column++
+		}
+		endColumn := column - 1
+
+		numbers := extractNumbers(transposed, startColumn, endColumn, operationRow)
+		operationRowStr := extractRowFromColumns(transposed, operationRow, startColumn, endColumn)
+		operation := extractOperation(operationRowStr)
+
+		if len(numbers) > 0 && operation != 0 {
+			result := applyOperation(numbers, operation)
+			total += result
+		}
+	}
+
+	return total
+}
+
+func PartTwo(data []string) int {
+	operationRow := len(data) - 1
+	transposed := transpose(data)
+
+	total := 0
+	column := len(transposed) - 1
+
+	for column >= 0 {
+		if isSpaceColumn(transposed[column]) {
+			column--
+			continue
+		}
+
+		endColumn := column
+		for column >= 0 && !isSpaceColumn(transposed[column]) {
+			column--
+		}
+		startColumn := column + 1
+
+		numbers := make([]int, 0)
+		for column := startColumn; column <= endColumn && column < len(transposed); column++ {
+			if number, ok := extractNumberFromColumn(transposed[column], operationRow); ok {
+				numbers = append(numbers, number)
+			}
+		}
+
+		operationRowStr := extractRowFromColumns(transposed, operationRow, startColumn, endColumn)
+		operation := extractOperation(operationRowStr)
+
+		if len(numbers) > 0 && operation != 0 {
+			result := applyOperation(numbers, operation)
+			total += result
+		}
+	}
+
+	return total
+}

internal/2025/DaySix/code_test.go

@@ -0,0 +1,26 @@
+package daysix
+
+import "testing"
+
+var testInput = []string{
+	"123 328  51 64 ",
+	" 45 64  387 23 ",
+	"  6 98  215 314",
+	"*   +   *   +  ",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 4277556
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 3263827
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DayTen/code.go

@@ -0,0 +1,91 @@
+package dayten
+
+import (
+	"advent-of-code/internal/registry"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+func init() {
+	registry.Register("2025D10", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(string(content), "\n")
+}
+
+func parseMachine(line string) ([]bool, [][]int) {
+	bracketRegex := regexp.MustCompile(`\[([.#]+)\]`)
+	parenthesisRegex := regexp.MustCompile(`\(([^)]+)\)`)
+
+	bracketMatch := bracketRegex.FindStringSubmatch(line)
+	targetString := bracketMatch[1]
+	target := make([]bool, len(targetString))
+	for idx, char := range targetString {
+		target[idx] = char == '#'
+	}
+
+	parenthesisMatches := parenthesisRegex.FindAllStringSubmatch(line, -1)
+	buttons := make([][]int, 0, len(parenthesisMatches))
+
+	for _, match := range parenthesisMatches {
+		buttonString := match[1]
+		parts := strings.Split(buttonString, ",")
+		button := make([]int, 0, len(parts))
+		for _, part := range parts {
+			light, _ := strconv.Atoi(part)
+			button = append(button, light)
+		}
+		buttons = append(buttons, button)
+	}
+
+	return target, buttons
+}
+
+func PartOne(data []string) int {
+	total := 0
+	for _, line := range data {
+		target, buttons := parseMachine(line)
+		numberOfLights := len(target)
+		numberOfButtons := len(buttons)
+		minimumPresses := numberOfButtons + 1
+
+		for mask := 0; mask < (1 << numberOfButtons); mask++ {
+			lights := make([]bool, numberOfLights)
+			presses := 0
+
+			for buttonIdx := range numberOfButtons {
+				if mask&(1<<buttonIdx) != 0 {
+					presses++
+					for _, light := range buttons[buttonIdx] {
+						if light < numberOfLights {
+							lights[light] = !lights[light]
+						}
+					}
+				}
+			}
+
+			matches := true
+			for idx := range numberOfLights {
+				if lights[idx] != target[idx] {
+					matches = false
+					break
+				}
+			}
+
+			if matches && presses < minimumPresses {
+				minimumPresses = presses
+			}
+		}
+		total += minimumPresses
+	}
+
+	return total
+}
+
+func PartTwo(data []string) int {
+	return 0
+}

internal/2025/DayTen/code_test.go

@@ -0,0 +1,25 @@
+package dayten
+
+import "testing"
+
+var testInput = []string{
+	"[.##.] (3) (1,3) (2) (2,3) (0,2) (0,1) {3,5,4,7}",
+	"[...#.] (0,2,3,4) (2,3) (0,4) (0,1,2) (1,2,3,4) {7,5,12,7,2}",
+	"[.###.#] (0,1,2,3,4) (0,3,4) (0,1,2,4,5) (1,2) {10,11,11,5,10,5}",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 7
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 33
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DayThree/code.go

@@ -0,0 +1,72 @@
+package daythree
+
+import (
+	"os"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2025D3", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) [][]int {
+	content, _ := os.ReadFile(filepath)
+	lines := strings.Split(string(content), "\n")
+	var data [][]int
+	for _, line := range lines {
+		var bank []int
+		for _, char := range line {
+			bank = append(bank, int(char-'0'))
+		}
+		data = append(data, bank)
+	}
+	return data
+}
+
+func PartOne(data [][]int) int {
+	total := 0
+	for _, bank := range data {
+		maxAfter := make([]int, len(bank))
+
+		for idx := len(bank) - 2; idx >= 0; idx-- {
+			maxAfter[idx] = max(maxAfter[idx+1], bank[idx+1])
+		}
+
+		maxJoltage := 0
+
+		for idx := 0; idx < len(bank)-1; idx++ {
+			joltage := bank[idx]*10 + maxAfter[idx]
+			maxJoltage = max(maxJoltage, joltage)
+		}
+		total += maxJoltage
+	}
+	return total
+}
+
+func PartTwo(data [][]int) int {
+	total := 0
+	for _, bank := range data {
+		var joltage int
+		start := 0
+
+		for position := range 12 {
+			remaining := 12 - position - 1
+			maxIdx := start
+			maxValue := bank[start]
+
+			for idx := start; idx < len(bank)-remaining; idx++ {
+				if bank[idx] > maxValue {
+					maxValue = bank[idx]
+					maxIdx = idx
+				}
+			}
+
+			joltage = joltage*10 + maxValue
+			start = maxIdx + 1
+		}
+		total += joltage
+	}
+	return total
+}

internal/2025/DayThree/code_test.go

@@ -0,0 +1,26 @@
+package daythree
+
+import "testing"
+
+var testInput = [][]int{
+	{9, 8, 7, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 1, 1},
+	{8, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9},
+	{2, 3, 4, 2, 3, 4, 2, 3, 4, 2, 3, 4, 2, 7, 8},
+	{8, 1, 8, 1, 8, 1, 9, 1, 1, 1, 1, 2, 1, 1, 1},
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 357
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 3121910778619
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/DayTwo/code.go

@@ -0,0 +1,87 @@
+package daytwo
+
+import (
+	"os"
+	"strconv"
+	"strings"
+
+	"advent-of-code/internal/registry"
+)
+
+func init() {
+	registry.Register("2025D2", ParseInput, PartOne, PartTwo)
+}
+
+func ParseInput(filepath string) []string {
+	content, _ := os.ReadFile(filepath)
+	return strings.Split(strings.TrimSpace(string(content)), "\n")
+}
+
+func PartOne(data []string) int {
+	sum := 0
+	for _, line := range data {
+		for newRange := range strings.SplitSeq(line, ",") {
+			parts := strings.Split(newRange, "-")
+			start, _ := strconv.Atoi(parts[0])
+			end, _ := strconv.Atoi(parts[1])
+			for id := start; id <= end; id++ {
+				sID := strconv.Itoa(id)
+				if len(sID)%2 == 0 {
+					half := len(sID) / 2
+					if sID[:half] == sID[half:] {
+						sum += id
+					}
+				}
+			}
+		}
+	}
+	return sum
+}
+
+func PartTwo(data []string) int {
+	totalSum := 0
+	for _, line := range data {
+		for rangeSpec := range strings.SplitSeq(line, ",") {
+			rangeStartStr, rangeEndStr, _ := strings.Cut(rangeSpec, "-")
+			rangeStart, _ := strconv.Atoi(rangeStartStr)
+			rangeEnd, _ := strconv.Atoi(rangeEndStr)
+
+			seenNumbers := make(map[int]bool)
+			maxDigits := len(rangeEndStr)
+
+			var generatePatterns func(string, int, int)
+			generatePatterns = func(currentPattern string, targetPatternLength, currentDepth int) {
+				if currentDepth == targetPatternLength {
+					repeated := currentPattern + currentPattern
+					for len(repeated) <= maxDigits {
+						number, err := strconv.Atoi(repeated)
+						if err != nil || number > rangeEnd {
+							break
+						}
+						if number >= rangeStart && !seenNumbers[number] {
+							totalSum += number
+							seenNumbers[number] = true
+						}
+						repeated += currentPattern
+					}
+					return
+				}
+
+				minDigit := 0
+				if currentDepth == 0 {
+					minDigit = 1
+				}
+
+				for digit := minDigit; digit <= 9; digit++ {
+					extendedPattern := currentPattern + strconv.Itoa(digit)
+					generatePatterns(extendedPattern, targetPatternLength, currentDepth+1)
+				}
+			}
+
+			for patternLength := 1; patternLength <= maxDigits/2; patternLength++ {
+				generatePatterns("", patternLength, 0)
+			}
+		}
+	}
+	return totalSum
+}

internal/2025/DayTwo/code_test.go

@@ -0,0 +1,33 @@
+package daytwo
+
+import "testing"
+
+var testInput = []string{
+	"11-22",
+	"95-115",
+	"998-1012",
+	"1188511880-1188511890",
+	"222220-222224",
+	"1698522-1698528",
+	"446443-446449",
+	"38593856-38593862",
+	"565653-565659",
+	"824824821-824824827",
+	"2121212118-2121212124",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 1227775554
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 4174379265
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}

internal/2025/register.go

@@ -0,0 +1,14 @@
+package year2025
+
+import (
+	_ "advent-of-code/internal/2025/DayEight"
+	_ "advent-of-code/internal/2025/DayFive"
+	_ "advent-of-code/internal/2025/DayFour"
+	_ "advent-of-code/internal/2025/DayNine"
+	_ "advent-of-code/internal/2025/DayOne"
+	_ "advent-of-code/internal/2025/DaySeven"
+	_ "advent-of-code/internal/2025/DaySix"
+	_ "advent-of-code/internal/2025/DayTen"
+	_ "advent-of-code/internal/2025/DayThree"
+	_ "advent-of-code/internal/2025/DayTwo"
+)

internal/data/2015/DayEight/input.txt

@@ -0,0 +1,300 @@
+"\xa8br\x8bjr\""
+"nq"
+"zjrfcpbktjmrzgsz\xcaqsc\x03n\"huqab"
+"daz\\zyyxddpwk"
+"draes\xa2n\\g\x27ek\"lj\"\\viqych"
+"nnx\\krnrfomdnt\x2flbl\xd2xpo\"cp\"k"
+"kwdaapalq"
+"u\"ptk"
+"ckhorczuiudfjmmcc\\u\"wozqxibsfjma"
+"ydctdrxat\"pd\"lwi\"bjesevfw\xe8"
+"v\"\xa8rrzep\"\"r"
+"nbydghkfvmq\\\xe0\"lfsrsvlsj\"i\x61liif"
+"jsas\"u"
+"odipikxlo"
+"\"rnubsgwltqkbsu\"pcpcs"
+"eitk\\f\\mhcqqoym\\ji"
+"vnedc"
+"\"lhcaurdqzyjyu"
+"haxzsa\"zcn\"y\"foclgtjfcnv\"m\x68krc"
+"\"eoeggg\"tmiydvcay\"vfavc"
+"snqvyqoncwxcvwbdktoywch"
+"rnfgjsyr\xd5wacy"
+"ik\"hebrpvsts"
+"txw"
+"\x15pxtdkogd\"urbm\"gevhh\"nxr\x3erxtk"
+"cetqtcy"
+"inleep\\mgl"
+"uflwbxvww\x2cxzezqnaply\"yh\"qlllzk"
+"eepak\"xqtedzt"
+"na\x61qzfieafvyrsnwkssznohjmc"
+"yceaonylz\xc1\\jrlbbkzwsidfi"
+"ybqafngkcqpbp"
+"\xaft"
+"yidjpaobqydso"
+"ju\\ldxig\\lrdrhjcmm\x77rc"
+"tylacqeslnwj\x48ds\"tjxa"
+"efbfm"
+"\\fxkgoprgdcjgyajykg\\dtbrz"
+"eujvva"
+"h\x7acwfpikme\\vwthyvrqdnx\""
+"rbpbrxm\\\"\"\"voxx"
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+"cyxdpkh\\\""
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+"tbxdzzllarlo"
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+"\x28hfxnfpycmpnkku\"csuf\xaarxlqyg\"x"
+"\"zvz\\rmg\"\\sxxoifffyqfyn\"iq\"ps"
+"\"z"
+"zbwkmk\"sgzos\x93gtc\""
+"bvm\x28aa\\\\\"pywuhaniox\\z\\hbp\xd7mold"
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+"\"f"
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+"hxilg\\"
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+"\\h"
+"qekfrc\xf6wduodbwrguqcng\\n"
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internal/data/2015/DayEleven/input.txt

@@ -0,0 +1 @@
+hxbxwxba

internal/data/2015/DayFour/input.txt

@@ -0,0 +1 @@
+iwrupvqb

internal/data/2015/DayFourteen/input.txt

@@ -0,0 +1,9 @@
+Vixen can fly 19 km/s for 7 seconds, but then must rest for 124 seconds.
+Rudolph can fly 3 km/s for 15 seconds, but then must rest for 28 seconds.
+Donner can fly 19 km/s for 9 seconds, but then must rest for 164 seconds.
+Blitzen can fly 19 km/s for 9 seconds, but then must rest for 158 seconds.
+Comet can fly 13 km/s for 7 seconds, but then must rest for 82 seconds.
+Cupid can fly 25 km/s for 6 seconds, but then must rest for 145 seconds.
+Dasher can fly 14 km/s for 3 seconds, but then must rest for 38 seconds.
+Dancer can fly 3 km/s for 16 seconds, but then must rest for 37 seconds.
+Prancer can fly 25 km/s for 6 seconds, but then must rest for 143 seconds.

internal/data/2015/DayNine/input.txt

@@ -0,0 +1,28 @@
+Tristram to AlphaCentauri = 34
+Tristram to Snowdin = 100
+Tristram to Tambi = 63
+Tristram to Faerun = 108
+Tristram to Norrath = 111
+Tristram to Straylight = 89
+Tristram to Arbre = 132
+AlphaCentauri to Snowdin = 4
+AlphaCentauri to Tambi = 79
+AlphaCentauri to Faerun = 44
+AlphaCentauri to Norrath = 147
+AlphaCentauri to Straylight = 133
+AlphaCentauri to Arbre = 74
+Snowdin to Tambi = 105
+Snowdin to Faerun = 95
+Snowdin to Norrath = 48
+Snowdin to Straylight = 88
+Snowdin to Arbre = 7
+Tambi to Faerun = 68
+Tambi to Norrath = 134
+Tambi to Straylight = 107
+Tambi to Arbre = 40
+Faerun to Norrath = 11
+Faerun to Straylight = 66
+Faerun to Arbre = 144
+Norrath to Straylight = 115
+Norrath to Arbre = 135
+Straylight to Arbre = 127

internal/data/2015/DaySeven/input.txt

@@ -0,0 +1,339 @@
+af AND ah -> ai
+NOT lk -> ll
+hz RSHIFT 1 -> is
+NOT go -> gp
+du OR dt -> dv
+x RSHIFT 5 -> aa
+at OR az -> ba
+eo LSHIFT 15 -> es
+ci OR ct -> cu
+b RSHIFT 5 -> f
+fm OR fn -> fo
+NOT ag -> ah
+v OR w -> x
+g AND i -> j
+an LSHIFT 15 -> ar
+1 AND cx -> cy
+jq AND jw -> jy
+iu RSHIFT 5 -> ix
+gl AND gm -> go
+NOT bw -> bx
+jp RSHIFT 3 -> jr
+hg AND hh -> hj
+bv AND bx -> by
+er OR es -> et
+kl OR kr -> ks
+et RSHIFT 1 -> fm
+e AND f -> h
+u LSHIFT 1 -> ao
+he RSHIFT 1 -> hx
+eg AND ei -> ej
+bo AND bu -> bw
+dz OR ef -> eg
+dy RSHIFT 3 -> ea
+gl OR gm -> gn
+da LSHIFT 1 -> du
+au OR av -> aw
+gj OR gu -> gv
+eu OR fa -> fb
+lg OR lm -> ln
+e OR f -> g
+NOT dm -> dn
+NOT l -> m
+aq OR ar -> as
+gj RSHIFT 5 -> gm
+hm AND ho -> hp
+ge LSHIFT 15 -> gi
+jp RSHIFT 1 -> ki
+hg OR hh -> hi
+lc LSHIFT 1 -> lw
+km OR kn -> ko
+eq LSHIFT 1 -> fk
+1 AND am -> an
+gj RSHIFT 1 -> hc
+aj AND al -> am
+gj AND gu -> gw
+ko AND kq -> kr
+ha OR gz -> hb
+bn OR by -> bz
+iv OR jb -> jc
+NOT ac -> ad
+bo OR bu -> bv
+d AND j -> l
+bk LSHIFT 1 -> ce
+de OR dk -> dl
+dd RSHIFT 1 -> dw
+hz AND ik -> im
+NOT jd -> je
+fo RSHIFT 2 -> fp
+hb LSHIFT 1 -> hv
+lf RSHIFT 2 -> lg
+gj RSHIFT 3 -> gl
+ki OR kj -> kk
+NOT ak -> al
+ld OR le -> lf
+ci RSHIFT 3 -> ck
+1 AND cc -> cd
+NOT kx -> ky
+fp OR fv -> fw
+ev AND ew -> ey
+dt LSHIFT 15 -> dx
+NOT ax -> ay
+bp AND bq -> bs
+NOT ii -> ij
+ci AND ct -> cv
+iq OR ip -> ir
+x RSHIFT 2 -> y
+fq OR fr -> fs
+bn RSHIFT 5 -> bq
+0 -> c
+14146 -> b
+d OR j -> k
+z OR aa -> ab
+gf OR ge -> gg
+df OR dg -> dh
+NOT hj -> hk
+NOT di -> dj
+fj LSHIFT 15 -> fn
+lf RSHIFT 1 -> ly
+b AND n -> p
+jq OR jw -> jx
+gn AND gp -> gq
+x RSHIFT 1 -> aq
+ex AND ez -> fa
+NOT fc -> fd
+bj OR bi -> bk
+as RSHIFT 5 -> av
+hu LSHIFT 15 -> hy
+NOT gs -> gt
+fs AND fu -> fv
+dh AND dj -> dk
+bz AND cb -> cc
+dy RSHIFT 1 -> er
+hc OR hd -> he
+fo OR fz -> ga
+t OR s -> u
+b RSHIFT 2 -> d
+NOT jy -> jz
+hz RSHIFT 2 -> ia
+kk AND kv -> kx
+ga AND gc -> gd
+fl LSHIFT 1 -> gf
+bn AND by -> ca
+NOT hr -> hs
+NOT bs -> bt
+lf RSHIFT 3 -> lh
+au AND av -> ax
+1 AND gd -> ge
+jr OR js -> jt
+fw AND fy -> fz
+NOT iz -> ja
+c LSHIFT 1 -> t
+dy RSHIFT 5 -> eb
+bp OR bq -> br
+NOT h -> i
+1 AND ds -> dt
+ab AND ad -> ae
+ap LSHIFT 1 -> bj
+br AND bt -> bu
+NOT ca -> cb
+NOT el -> em
+s LSHIFT 15 -> w
+gk OR gq -> gr
+ff AND fh -> fi
+kf LSHIFT 15 -> kj
+fp AND fv -> fx
+lh OR li -> lj
+bn RSHIFT 3 -> bp
+jp OR ka -> kb
+lw OR lv -> lx
+iy AND ja -> jb
+dy OR ej -> ek
+1 AND bh -> bi
+NOT kt -> ku
+ao OR an -> ap
+ia AND ig -> ii
+NOT ey -> ez
+bn RSHIFT 1 -> cg
+fk OR fj -> fl
+ce OR cd -> cf
+eu AND fa -> fc
+kg OR kf -> kh
+jr AND js -> ju
+iu RSHIFT 3 -> iw
+df AND dg -> di
+dl AND dn -> do
+la LSHIFT 15 -> le
+fo RSHIFT 1 -> gh
+NOT gw -> gx
+NOT gb -> gc
+ir LSHIFT 1 -> jl
+x AND ai -> ak
+he RSHIFT 5 -> hh
+1 AND lu -> lv
+NOT ft -> fu
+gh OR gi -> gj
+lf RSHIFT 5 -> li
+x RSHIFT 3 -> z
+b RSHIFT 3 -> e
+he RSHIFT 2 -> hf
+NOT fx -> fy
+jt AND jv -> jw
+hx OR hy -> hz
+jp AND ka -> kc
+fb AND fd -> fe
+hz OR ik -> il
+ci RSHIFT 1 -> db
+fo AND fz -> gb
+fq AND fr -> ft
+gj RSHIFT 2 -> gk
+cg OR ch -> ci
+cd LSHIFT 15 -> ch
+jm LSHIFT 1 -> kg
+ih AND ij -> ik
+fo RSHIFT 3 -> fq
+fo RSHIFT 5 -> fr
+1 AND fi -> fj
+1 AND kz -> la
+iu AND jf -> jh
+cq AND cs -> ct
+dv LSHIFT 1 -> ep
+hf OR hl -> hm
+km AND kn -> kp
+de AND dk -> dm
+dd RSHIFT 5 -> dg
+NOT lo -> lp
+NOT ju -> jv
+NOT fg -> fh
+cm AND co -> cp
+ea AND eb -> ed
+dd RSHIFT 3 -> df
+gr AND gt -> gu
+ep OR eo -> eq
+cj AND cp -> cr
+lf OR lq -> lr
+gg LSHIFT 1 -> ha
+et RSHIFT 2 -> eu
+NOT jh -> ji
+ek AND em -> en
+jk LSHIFT 15 -> jo
+ia OR ig -> ih
+gv AND gx -> gy
+et AND fe -> fg
+lh AND li -> lk
+1 AND io -> ip
+kb AND kd -> ke
+kk RSHIFT 5 -> kn
+id AND if -> ig
+NOT ls -> lt
+dw OR dx -> dy
+dd AND do -> dq
+lf AND lq -> ls
+NOT kc -> kd
+dy AND ej -> el
+1 AND ke -> kf
+et OR fe -> ff
+hz RSHIFT 5 -> ic
+dd OR do -> dp
+cj OR cp -> cq
+NOT dq -> dr
+kk RSHIFT 1 -> ld
+jg AND ji -> jj
+he OR hp -> hq
+hi AND hk -> hl
+dp AND dr -> ds
+dz AND ef -> eh
+hz RSHIFT 3 -> ib
+db OR dc -> dd
+hw LSHIFT 1 -> iq
+he AND hp -> hr
+NOT cr -> cs
+lg AND lm -> lo
+hv OR hu -> hw
+il AND in -> io
+NOT eh -> ei
+gz LSHIFT 15 -> hd
+gk AND gq -> gs
+1 AND en -> eo
+NOT kp -> kq
+et RSHIFT 5 -> ew
+lj AND ll -> lm
+he RSHIFT 3 -> hg
+et RSHIFT 3 -> ev
+as AND bd -> bf
+cu AND cw -> cx
+jx AND jz -> ka
+b OR n -> o
+be AND bg -> bh
+1 AND ht -> hu
+1 AND gy -> gz
+NOT hn -> ho
+ck OR cl -> cm
+ec AND ee -> ef
+lv LSHIFT 15 -> lz
+ks AND ku -> kv
+NOT ie -> if
+hf AND hl -> hn
+1 AND r -> s
+ib AND ic -> ie
+hq AND hs -> ht
+y AND ae -> ag
+NOT ed -> ee
+bi LSHIFT 15 -> bm
+dy RSHIFT 2 -> dz
+ci RSHIFT 2 -> cj
+NOT bf -> bg
+NOT im -> in
+ev OR ew -> ex
+ib OR ic -> id
+bn RSHIFT 2 -> bo
+dd RSHIFT 2 -> de
+bl OR bm -> bn
+as RSHIFT 1 -> bl
+ea OR eb -> ec
+ln AND lp -> lq
+kk RSHIFT 3 -> km
+is OR it -> iu
+iu RSHIFT 2 -> iv
+as OR bd -> be
+ip LSHIFT 15 -> it
+iw OR ix -> iy
+kk RSHIFT 2 -> kl
+NOT bb -> bc
+ci RSHIFT 5 -> cl
+ly OR lz -> ma
+z AND aa -> ac
+iu RSHIFT 1 -> jn
+cy LSHIFT 15 -> dc
+cf LSHIFT 1 -> cz
+as RSHIFT 3 -> au
+cz OR cy -> da
+kw AND ky -> kz
+lx -> a
+iw AND ix -> iz
+lr AND lt -> lu
+jp RSHIFT 5 -> js
+aw AND ay -> az
+jc AND je -> jf
+lb OR la -> lc
+NOT cn -> co
+kh LSHIFT 1 -> lb
+1 AND jj -> jk
+y OR ae -> af
+ck AND cl -> cn
+kk OR kv -> kw
+NOT cv -> cw
+kl AND kr -> kt
+iu OR jf -> jg
+at AND az -> bb
+jp RSHIFT 2 -> jq
+iv AND jb -> jd
+jn OR jo -> jp
+x OR ai -> aj
+ba AND bc -> bd
+jl OR jk -> jm
+b RSHIFT 1 -> v
+o AND q -> r
+NOT p -> q
+k AND m -> n
+as RSHIFT 2 -> at

internal/data/2015/DaySix/input.txt

@@ -0,0 +1,300 @@
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+turn off 820,516 through 871,914
+turn off 427,423 through 929,502
+turn on 774,14 through 977,877
+turn on 410,146 through 864,337
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internal/data/2015/DayTen/input.txt

@@ -0,0 +1 @@
+1113122113

internal/data/2015/DayThirteen/input.txt

@@ -0,0 +1,56 @@
+Alice would lose 57 happiness units by sitting next to Bob.
+Alice would lose 62 happiness units by sitting next to Carol.
+Alice would lose 75 happiness units by sitting next to David.
+Alice would gain 71 happiness units by sitting next to Eric.
+Alice would lose 22 happiness units by sitting next to Frank.
+Alice would lose 23 happiness units by sitting next to George.
+Alice would lose 76 happiness units by sitting next to Mallory.
+Bob would lose 14 happiness units by sitting next to Alice.
+Bob would gain 48 happiness units by sitting next to Carol.
+Bob would gain 89 happiness units by sitting next to David.
+Bob would gain 86 happiness units by sitting next to Eric.
+Bob would lose 2 happiness units by sitting next to Frank.
+Bob would gain 27 happiness units by sitting next to George.
+Bob would gain 19 happiness units by sitting next to Mallory.
+Carol would gain 37 happiness units by sitting next to Alice.
+Carol would gain 45 happiness units by sitting next to Bob.
+Carol would gain 24 happiness units by sitting next to David.
+Carol would gain 5 happiness units by sitting next to Eric.
+Carol would lose 68 happiness units by sitting next to Frank.
+Carol would lose 25 happiness units by sitting next to George.
+Carol would gain 30 happiness units by sitting next to Mallory.
+David would lose 51 happiness units by sitting next to Alice.
+David would gain 34 happiness units by sitting next to Bob.
+David would gain 99 happiness units by sitting next to Carol.
+David would gain 91 happiness units by sitting next to Eric.
+David would lose 38 happiness units by sitting next to Frank.
+David would gain 60 happiness units by sitting next to George.
+David would lose 63 happiness units by sitting next to Mallory.
+Eric would gain 23 happiness units by sitting next to Alice.
+Eric would lose 69 happiness units by sitting next to Bob.
+Eric would lose 33 happiness units by sitting next to Carol.
+Eric would lose 47 happiness units by sitting next to David.
+Eric would gain 75 happiness units by sitting next to Frank.
+Eric would gain 82 happiness units by sitting next to George.
+Eric would gain 13 happiness units by sitting next to Mallory.
+Frank would gain 77 happiness units by sitting next to Alice.
+Frank would gain 27 happiness units by sitting next to Bob.
+Frank would lose 87 happiness units by sitting next to Carol.
+Frank would gain 74 happiness units by sitting next to David.
+Frank would lose 41 happiness units by sitting next to Eric.
+Frank would lose 99 happiness units by sitting next to George.
+Frank would gain 26 happiness units by sitting next to Mallory.
+George would lose 63 happiness units by sitting next to Alice.
+George would lose 51 happiness units by sitting next to Bob.
+George would lose 60 happiness units by sitting next to Carol.
+George would gain 30 happiness units by sitting next to David.
+George would lose 100 happiness units by sitting next to Eric.
+George would lose 63 happiness units by sitting next to Frank.
+George would gain 57 happiness units by sitting next to Mallory.
+Mallory would lose 71 happiness units by sitting next to Alice.
+Mallory would lose 28 happiness units by sitting next to Bob.
+Mallory would lose 10 happiness units by sitting next to Carol.
+Mallory would gain 44 happiness units by sitting next to David.
+Mallory would gain 22 happiness units by sitting next to Eric.
+Mallory would gain 79 happiness units by sitting next to Frank.
+Mallory would lose 16 happiness units by sitting next to George.

internal/data/2016/DayFive/input.txt

@@ -0,0 +1 @@
+reyedfim