Advent of Code 2024

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Overview

This repository contains my solutions for "Advent of Code 2024".

Getting started

Required tools:

• Bazelisk - used to manage Bazel, which in turn is used to manage all compilers, dependencies, libraries and binaries, and their tasks.

• Rust - The Rust programming language (the toolchain itself is managed by Bazel, but you will likely need a local copy in order to use with your IDE/editor)

Basics

• Run a single day: bazel run --config=release //day_<day number> \-- <args>

• Run tests for a single day: bazel test //day_<day number>:all

• If you update any of the dependencies, you will need to regenerate the crate index. To do that, run the following command: CARGO_BAZEL_REPIN=1 bazel sync --only=crates

Bootstrapping a new day

To add a new day to the repository, follow this list of instructions:

1. Run cargo new day_<day number> --bin. This should produce a new folder for the source code of that day, as well as add it to the root Cargo.toml.

2. Add an entry for the new folder to the MODULE.bazel file in the crates.from_cargo manifests. This will allow Bazel to graph and build the dependencies for the binary, as well as the binary itself.

3. Add any basic dependencies to the day's Cargo.toml. Most days use the shared aocutils library, as well as dependencies like clap and itertools.

[dependencies]
aocutils = { path = "../aocutils" }
clap = { version = "4.5.22", features = ["derive", "cargo"] }
itertools = { version = "0.13.0" }

4. Create a BUILD file for the new day. You can use the other day's build files as a template, but it should generally look something like this:

load("@crates//:defs.bzl", "all_crate_deps")
load("@rules_rust//rust:defs.bzl", "rust_binary")

rust_binary(
    name = "day_<day number>",
    srcs = ["src/main.rs"],
    data = glob(["inputs/*.txt"]),
    deps = [
        "//aocutils",
    ] + all_crate_deps(normal = True),
)

5. Bootstrap the basic day solving program - most days start off the same, so starting off with the common main is a good idea.

use clap::Parser;
use std::{env, path};

#[derive(Parser, Debug)]
#[command(version, about, long_about = None)]
struct Args {
    #[arg(short, long, default_value = "example.txt")]
    input: String,
}

fn main() {
    let args = Args::parse();
    let crate_name = clap::crate_name!();
    let cli_inputpath = path::Path::new(&args.input);

    println!("Hello to solver for {crate_name}");

    // TODO: (Stefan) Solve today's problem! ⭐⭐
}

6. Create a subfolder in the day called inputs with example.txt as a file. This file can then be filled with the example input given by Advent of Code.

7. Resync all dependencies - only needs to be done once, since we are adding a new target.

CARGO_BAZEL_REPIN=1 bazel sync --only=crates

8. Build and run the new day

bazel run --config=debug //day_<day number> -- --input="example.txt"