test: add unit test

2020/day02/go.mod

@@ -0,0 +1,3 @@
+module 2020/day02
+
+go 1.25.4

2020/day02/main.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func parseInput(file string) []string {
+	content, err := os.ReadFile(file)
+	if err != nil {
+		log.Fatalf("Failed to read input file: %v", err)
+	}
+	lines := strings.Split(string(content), "\n")
+	var data []string
+	for _, line := range lines {
+		data = append(data, line)
+	}
+	return data
+}
+
+func PartOne(data []string) int {
+	valid := 0
+	for _, line := range data {
+		if line == "" {
+			continue
+		}
+		parts := strings.Split(line, ": ")
+		policy := parts[0]
+		password := parts[1]
+
+		policyParts := strings.Split(policy, " ")
+		rangeStr := policyParts[0]
+		letter := policyParts[1]
+
+		rangeParts := strings.Split(rangeStr, "-")
+		min, _ := strconv.Atoi(rangeParts[0])
+		max, _ := strconv.Atoi(rangeParts[1])
+
+		count := strings.Count(password, letter)
+		if count >= min && count <= max {
+			valid++
+		}
+	}
+	return valid
+}
+
+func PartTwo(data []string) int {
+	valid := 0
+	for _, line := range data {
+		if line == "" {
+			continue
+		}
+		parts := strings.Split(line, ": ")
+		policy := parts[0]
+		password := parts[1]
+
+		policyParts := strings.Split(policy, " ")
+		rangeStr := policyParts[0]
+		letter := policyParts[1]
+
+		rangeParts := strings.Split(rangeStr, "-")
+		firstPosition, _ := strconv.Atoi(rangeParts[0])
+		secondPosition, _ := strconv.Atoi(rangeParts[1])
+
+		atFirstPosition := len(password) >= firstPosition && password[firstPosition-1] == letter[0]
+		atSecondPosition := len(password) >= secondPosition && password[secondPosition-1] == letter[0]
+
+		if atFirstPosition != atSecondPosition {
+			valid++
+		}
+	}
+	return valid
+}
+
+func main() {
+	data := parseInput("input.txt")
+	fmt.Println("Part 1:", PartOne(data))
+	fmt.Println("Part 2:", PartTwo(data))
+}

2020/day02/main_test.go

@@ -0,0 +1,29 @@
+package main
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	input := []string{
+		"1-3 a: abcde",
+		"1-3 b: cdefg",
+		"2-9 c: ccccccccc",
+	}
+	expected := 2
+	got := PartOne(input)
+	if got != expected {
+		t.Errorf("PartOne(%v) = %d, want %d", input, got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	input := []string{
+		"1-3 a: abcde",
+		"1-3 b: cdefg",
+		"2-9 c: ccccccccc",
+	}
+	expected := 1
+	got := PartTwo(input)
+	if got != expected {
+		t.Errorf("PartOne(%v) = %d, want %d", input, got, expected)
+	}
+}