Advent of Code Template (Rust)

Advent of Code Rust Template

This repository provides a structured Rust workspace for solving Advent of Code puzzles.
The layout is designed to stay manageable across all AoC days while keeping the code easy to navigate and extend.

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Workspace Structure

aoc-lib/
├── lib.rs                # Year/day registry
├── year2024.rs           # Example year module
├── year2024/
│   └── day01.rs          # Example solution
└── utils/
    ├── mod.rs
    ├── input.rs          # Local + remote input loading
    └── output.rs         # Formatting helpers

aoc/
├── main.rs               # Run/list/download commands
└── bin/
    └── new-day.rs        # Generates year/day modules (prints lib.rs updates)

benches/
└── all_days.rs           # Criterion benchmarks

If you’ve worked with Rust workspaces before, the overall layout should feel straightforward.

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Prerequisites

• A Rust toolchain (rustup recommended)
• An Advent of Code account
• Your personal AoC session cookie (session=...)

How to get your AoC session cookie

1. Log in at https://adventofcode.com
2. Open developer tools → Network
3. Refresh the page
4. Select any request to adventofcode.com
5. Look at the cookie header
6. Copy the value that begins with session=

Export it:

export AOC_SESSION="paste_the_value_here"

Keep this value private and do not commit it.

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Setup

git clone https://github.com/sanctusgee/advent-of-code-rust-template
cd advent-of-code-rust-template
cargo build

After the initial build, you can start generating new years and days.

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Create a New Year / Day

Day 1 (for example, 2025)

cargo run - bin new-day 2025 1

This script:

• creates aoc-lib/src/year2025.rs if it doesn’t exist
• creates aoc-lib/src/year2025/day01.rs
• creates input/2025/day01/
• prints the exact lines to add to aoc-lib/src/lib.rs

Updating lib.rs is a manual step so you can control ordering and visibility.

Next day

cargo run - bin new-day 2025 2

Use the same command pattern for each new day.

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Download Inputs

cargo run - bin aoc download 2025 1

Inputs are stored under:

input/<year>/<day>/input.txt

They’re ignored by Git by default so you won’t commit personal data.

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Run a Solution

cargo run - bin aoc run 2025 1

List available solvers:

cargo run - bin aoc list

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Generated Day Scaffold

Each new day includes the same starter structure so you can focus directly on the puzzle:

use crate::utils;
use anyhow::Result;

pub fn solve() -> Result<()> {
 let input = utils::load_input(2025, 5)?;
 
 let part1 = solve_part1(&input)?;
 let part2 = solve_part2(&input)?;
 
 println!("Day 5 / Year 2025");
 println!("Part 1: {}", part1);
 println!("Part 2: {}", part2);
 
 Ok(())
}

fn solve_part1(input: &str) -> Result<impl std::fmt::Display> {
 Ok(0)
}

fn solve_part2(input: &str) -> Result<impl std::fmt::Display> {
 Ok(0)
}

The only convention is that each day exposes a solve() function returning anyhow::Result<()>.

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Testing

cargo test day02

You can place tests directly alongside each day’s solution module.

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Benchmarking (Optional)

cargo bench

Criterion will generate a report under:

target/criterion/report/index.html

Benchmarking can help when experimenting with different solution approaches.

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Dependencies

Core libraries:

• anyhow
• clap
• colored
• reqwest
• criterion

Optional utilities (commented out by default):

• regex
• itertools
• ahash
• atoi
• once_cell

The workspace passes:

cargo clippy --all-targets --all-features

without warnings to ensure a clean baseline.

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License

MIT