🎄 Advent of Code 2025

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 9	⭐

Usage

➡️ Scaffold a day

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

# output:
# Created module file "src/bin/01.rs"
# Created empty input file "data/inputs/01.txt"
# Created empty example file "data/examples/01.txt"
# ---
# 🎄 Type `cargo solve 01` to run your solution.

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

Important

This requires installing the aoc-cli crate.

You can automatically download puzzle input and description by either appending the --download flag to scaffold (e.g. cargo scaffold 4 --download) or with the separate download command:

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

# output:
# [INFO  aoc] 🎄 aoc-cli - Advent of Code command-line tool
# [INFO  aoc_client] 🎅 Saved puzzle to 'data/puzzles/01.md'
# [INFO  aoc_client] 🎅 Saved input to 'data/inputs/01.txt'
# ---
# 🎄 Successfully wrote input to "data/inputs/01.txt".
# 🎄 Successfully wrote puzzle to "data/puzzles/01.md".

➡️ Run solutions for a day

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

# output:
#     Finished dev [unoptimized + debuginfo] target(s) in 0.13s
#     Running `target/debug/01`
# Part 1: 42 (166.0ns)
# Part 2: 42 (41.0ns)

The solve command runs your solution against real puzzle inputs. To run an optimized build of your code, append the --release flag as with any other rust program.

Submitting solutions

Important

This requires installing the aoc-cli crate.

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

➡️ Run all solutions

cargo all

# output:
#     Running `target/release/advent_of_code`
# ----------
# | Day 01 |
# ----------
# Part 1: 42 (19.0ns)
# Part 2: 42 (19.0ns)
# <...other days...>
# Total: 0.20ms

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.

➡️ Benchmark your solutions

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

# output:
# Day 08
# ------
# Part 1: 1 (39.0ns @ 10000 samples)
# Part 2: 2 (39.0ns @ 10000 samples)
#
# Total (Run): 0.00ms
#
# Stored updated benchmarks.

The cargo time command allows you to benchmark your code and store timings in the readme. When benching, the runner will run your code between 10 and 10.000 times, depending on execution time of first execution, and print the average execution time.

cargo time has three modes of execution:

1. cargo time without arguments incrementally benches solutions that do not have been stored in the readme yet and skips the rest.
2. cargo time <day> benches a single solution.
3. cargo time --all benches all solutions.

By default, cargo time does not write to the readme. In order to do so, append the --store flag: cargo time --store.

Please note that these are not scientific benchmarks, understand them as a fun approximation. 😉 Timings, especially in the microseconds range, might change a bit between invocations.

➡️ Run all tests

cargo test

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.

➡️ Read puzzle description

Important

This command requires installing the aoc-cli crate.

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

# output:
# Loaded session cookie from "/Users/<snip>/.adventofcode.session".
# Fetching puzzle for day 1, 2022...
# ...the input...

➡️ Scaffold, download & read the current aoc day

Important

This command requires installing the aoc-cli crate.

During december, the today shorthand command can be used to:

• scaffold a solution for the current day
• download its input
• and read the puzzle

in one go.

# example: `cargo today` on December 1st
cargo today

# output:
# Created module file "src/bin/01.rs"
# Created empty input file "data/inputs/01.txt"
# Created empty example file "data/examples/01.txt"
# ---
# 🎄 Type `cargo solve 01` to run your solution.
# [INFO  aoc] 🎄 aoc-cli - Advent of Code command-line tool
# [INFO  aoc_client] 🎅 Saved puzzle to 'data/puzzles/01.md'
# [INFO  aoc_client] 🎅 Saved input to 'data/inputs/01.txt'
# ---
# 🎄 Successfully wrote input to "data/inputs/01.txt".
# 🎄 Successfully wrote puzzle to "data/puzzles/01.md".
#
# Loaded session cookie from "/Users/<snip>/.adventofcode.session".
# Fetching puzzle for day 1, 2022...
# ...the input...

➡️ Format code

cargo fmt

➡️ Lint code

cargo clippy