🎄 Advent of Code {year}

Solutions for Advent of Code in Rust.

2025 Results

Day	Part 1	Part 2
Day 1	⭐	⭐
Day 2	⭐	⭐
Day 3	⭐	⭐
Day 4	⭐	⭐
Day 5	⭐	⭐
Day 6	⭐	⭐
Day 7	⭐	⭐
Day 8	⭐	⭐
Day 9	⭐

Benchmarks

Day	Part 1	Part 2
Day 1	114.2µs	119.1µs
Day 2	137.7ms	110.4ms
Day 3	32.3µs	101.8µs
Day 4	1.0ms	29.4ms
Day 5	1.0ms	957.7µs
Day 6	61.0µs	281.3µs
Day 7	2.9ms	-

Total: 284.07ms

Usage

➡️ Scaffold a day

# example: `cargo scaffold 1`
cargo scaffold <day>

Individual solutions live in the ./src/bin/ directory as separate binaries. Inputs and examples live in the the ./data directory.

Every solution has tests referencing its example file in ./data/examples. Use these tests to develop and debug your solutions against the example input. In VS Code, rust-analyzer will display buttons for running / debugging these unit tests above the unit test blocks.

Tip

If a day has multiple example inputs, you can use the read_file_part() helper in your tests instead of read_file(). If this e.g. applies to day 1, you can create a second example file 01-2.txt and invoke the helper like let result = part_two(&advent_of_code::template::read_file_part("examples", DAY, 2));. This supports an arbitrary number of example files.

➡️ Download input for a day

# example: `cargo download 1`
cargo download <day>

➡️ Run solutions for a day

# example: `cargo solve 01`
cargo solve <day>

Submitting solutions

Append the --submit <part> option to the solve command to submit your solution for checking.

➡️ Run all solutions

This runs all solutions sequentially and prints output to the command-line. Same as for the solve command, the --release flag runs an optimized build.

cargo all

➡️ Benchmark your solutions

# example: `cargo time 8 --store`
cargo time <day> [--all] [--store]

➡️ Run all tests

To run tests for a specific day, append --bin <day>, e.g. cargo test --bin 01. You can further scope it down to a specific part, e.g. cargo test --bin 01 part_one.

cargo test

➡️ Format code

cargo fmt

➡️ Lint code

cargo clippy

Optional template features

Use DHAT to profile heap allocations

If you are not only interested in the runtime of your solution, but also its memory allocation profile, you can use the template's DHAT integration to analyze it. In order to activate DHAT, call the solve command with the --dhat flag.

cargo solve 1 --dhat

# output:
#     Running `target/dhat/1`
# dhat: Total:     276 bytes in 3 blocks
# dhat: At t-gmax: 232 bytes in 2 blocks
# dhat: At t-end:  0 bytes in 0 blocks
# dhat: The data has been saved to dhat-heap.json, and is viewable with dhat/dh_view.html
# Part 1: 9001 (4.1ms)

The command will output some basic stats to the command-line and generate a dhat-heap.json report in the repo root directory.

You can pass the report a tool like dh-view to view a detailed breakdown of heap allocations.

Useful crates

• itertools: Extends iterators with extra methods and adaptors. Frequently useful for aoc puzzles.
• regex: Official regular expressions implementation for Rust.

A curated list of popular crates can be found on blessed.rs.

Do you have aoc-specific crate recommendations? Share them!

Footnotes