138 lines
4.5 KiB
Markdown
138 lines
4.5 KiB
Markdown
# Advent of Code
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Personal solutions for [Advent of Code](https://adventofcode.com/), all implemented in Go.
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The goal is to practice programming and problem-solving habits while keeping each day's solution self-contained and easy to revisit later.
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It uses pure Go, no external dependencies.
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Also, it's a fresh start from 2025. I do some exercises from other years along the way, which explains why no year is complete and why everything is in "recent" Go.
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Ultimately, my goal is to complete all the years of Advent of Code here.
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## Requirements
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- Go 1.25
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- Puzzle input
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## Repository Structure
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```
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├── cmd/
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│ └── aoc/
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│ └── main.go # CLI entry point for running puzzles
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└── internal/
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├── 2020/
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│ ├── register.go # Aggregates import for main.go
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│ ├── DayOne/
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│ │ ├── code.go # Day 1 solution for 2020
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│ │ └── code_test.go # Unit tests for Day 1 solution
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│ └── ... # Other days for 2020
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├── 2021/
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│ └── ... # 2021 days code and tests
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├── registry/
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│ └── registry.go # Central map/registry for finding and running days
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└── data/
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├── 2020/
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│ ├── DayOne/
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│ │ └── input.txt # Puzzle input for Day 1 (2020)
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│ └── ... # Inputs for other days
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└── ... # Inputs for other years
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```
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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.
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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.
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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.
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### Starting a new day
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```bash
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make 2020D1
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```
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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.
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Then, it will create the following files:
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```bash
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internal/2020/DayOne/code.go
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internal/2020/DayOne/code_test.go
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```
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### Handling string answers
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Occasionally, a puzzle requires a string as the answer. However, my solution framework expects PartOne/PartTwo functions to return integers.
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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.
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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.
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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.
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## Usage
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Build the CLI tool:
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```bash
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make
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```
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Run a day's solution:
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```bash
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bin/aoc 2020D1 # Run both parts
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bin/aoc 2020D1P1 # Run only part one
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bin/aoc 2020D1P2 # Run only part two
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```
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Example output:
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```bash
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$ bin/aoc 2020D1
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197451
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138233720
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$ bin/aoc 2020D1P1
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197451
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$ bin/aoc 2020D1P2
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138233720
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```
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## Tests
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In the Advent of Code, every day the logic is explained with a sample result, like this:
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```
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For example:
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1abc2
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pqr3stu8vwx
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a1b2c3d4e5f
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treb7uchet
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In this example, the calibration values of these four lines are 12, 38, 15, and 77.
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Adding these together produces 142.
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```
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I'm using these examples each day to validate my logic.
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Run all tests:
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```bash
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make test
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```
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Or run tests for a specific day:
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```bash
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go test ./internal/2020/DayOne/...
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```
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## Notes
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Happy coding, and good luck on the puzzles!
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