2022/src/bin/day03.rs

use std::collections::HashSet;

use aoc_2022::*;

use color_eyre::eyre::Result;
use tracing::*;
use tracing_subscriber::EnvFilter;

type Input = Vec<(HashSet<i32>, HashSet<i32>)>;
type Output = i32;

fn part_1(input: &Input) -> Output {
    input
        .iter()
        .map(|(left, right)| left.intersection(right).sum::<i32>())
        .sum()
}

fn part_2(input: &Input) -> Output {
    input
        .iter()
        .map(|(left, right)| left.union(right).cloned().collect())
        .collect::<Vec<HashSet<i32>>>()
        .chunks(3)
        .map(|sets| {
            // debug!("Sets: {:?}", sets);
            sets.iter()
                .skip(1)
                .fold(sets[0].clone(), |acc, s| {
                    acc.intersection(s).cloned().collect()
                })
                .iter()
                .fold(0, |acc, x| acc + *x)
        })
        .sum()
}

fn parse_input(pathname: &str) -> Input {
    file_to_lines(pathname)
        .iter()
        .map(|line| {
            let mut left: HashSet<i32> = HashSet::new();
            let mut right: HashSet<i32> = HashSet::new();

            let mid = line.len() / 2;
            for (i, c) in line.chars().enumerate() {
                let s = if i < mid { &mut left } else { &mut right };

                s.insert(if c < 'a' {
                    c as i32 - 'A' as i32 + 27
                } else {
                    c as i32 - 'a' as i32 + 1
                });
            }

            (left, right)
        })
        .collect()
}

fn main() -> Result<()> {
    tracing_subscriber::fmt()
        .with_env_filter(EnvFilter::from_default_env())
        .with_target(false)
        .with_file(true)
        .with_line_number(true)
        .without_time()
        .compact()
        .init();
    color_eyre::install()?;

    let input = parse_input("inputs/day03.txt");

    info!("Part 1: {}", part_1(&input));
    info!("Part 2: {}", part_2(&input));

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_part_1() {
        let sample = parse_input("samples/day03.txt");
        assert_eq!(part_1(&sample), 157);
    }

    #[test]
    fn test_part_2() {
        let sample = parse_input("samples/day03.txt");
        assert_eq!(part_2(&sample), 70);
    }
}