Advent of Code 2022 in Rust, stdlib only.

01.rs

use std::{env, error::Error, fs};

fn main() -> Result<(), Box<dyn Error>> {
    let mut args = env::args();

    let _name = args.next().ok_or("no program name")?;
    let path = args.next().ok_or("missing path")?;

    let input = fs::read_to_string(path)?;
    let result = input
        .split_terminator("\n\n")
        .map(|s| {
            s.split_terminator('\n')
                .map(|s| s.parse::<i64>())
                .sum::<Result<i64, _>>()
        })
        .collect::<Result<Vec<_>, _>>()?
        .into_iter()
        .max()
        .ok_or("couldn't determine max")?;

    println!("{result}");

    Ok(())
}

README.txt

Advent of Code 2022 in Rust, stdlib only.

As a single file is used per day, with no external libraries `rustc` is used
without `cargo`. A helper script `cult` wraps `rustc` invocations in `cargo`ish
commands.

For example, to build and run day 1, run:

    ./cult 01 path/to/input.txt

cult

#!/bin/sh

# a terrible build tool that does none of the things cargo does

command="$1"
shift
name="$1"
shift

case "$command" in
  build)
    rustc --edition 2021 "$name".rs
    ;;
  run)
    rustc --edition 2021 "$name".rs && ./"$name" $@
    ;;
  fmt)
    rustfmt --edition 2021 "$name".rs
    ;;
  clippy)
    clippy-driver --edition 2021 "$name".rs
    ;;
  clean)
    rm "$name"
    ;;
  *)
    echo "unknown command"
    ;;
esac