day02.rs

use std::{cmp, fs};

pub(crate) fn day02() {
    println!("{}", part_a(fs::read_to_string("input/2023/day02/input.txt").unwrap()));
    println!("{}", part_b(fs::read_to_string("input/2023/day02/input.txt").unwrap()));
}

fn part_a(games: String) -> i32 {
    games.lines().map(|line| {
        let (id_str, cubes_str) = line.split_once(": ").unwrap();
        let id = &id_str[5..];

        for set_str in cubes_str.split("; ") {
            let mut red_total = 12;
            let mut green_total = 13;
            let mut blue_total = 14;

            for cube in set_str.split(", ") {
                let (num_str, color) = cube.split_once(" ").unwrap();
                let num = num_str.parse::<i32>().unwrap();

                match color {
                    "red" => { red_total -= num }
                    "green" => { green_total -= num }
                    "blue" => { blue_total -= num }
                    _ => panic!("unknown color {}", color)
                }

                if red_total < 0 || green_total < 0 || blue_total < 0 {
                    return 0;
                }
            }
        }

        id.parse().unwrap()
    }).sum()
}

fn part_b(games: String) -> i32 {
    games.lines().map(|line| {
        let (_, cubes_str) = line.split_once(": ").unwrap();

        let mut red_max = 0;
        let mut green_max = 0;
        let mut blue_max = 0;

        for set_str in cubes_str.split("; ") {
            for cube in set_str.split(", ") {
                let (num_str, color) = cube.split_once(" ").unwrap();
                let num = num_str.parse::<i32>().unwrap();

                match color {
                    "red" => { red_max = cmp::max(red_max, num) }
                    "green" => { green_max = cmp::max(green_max, num) }
                    "blue" => { blue_max = cmp::max(blue_max, num) }
                    _ => panic!("unknown color {}", color)
                }
            }
        }

        red_max * green_max * blue_max
    }).sum()
}

#[cfg(test)]
mod day02_tests {
    use std::fs;

    use crate::y2023::day02::{part_a, part_b};

    #[test]
    fn test_works() {
        let input_a = fs::read_to_string("input/2023/day02/test.txt").unwrap();
        assert_eq!(8, part_a(input_a));
        let input_b = fs::read_to_string("input/2023/day02/test.txt").unwrap();
        assert_eq!(2286, part_b(input_b));
    }

    #[test]
    fn input_works() {
        assert_eq!(2085, part_a(fs::read_to_string("input/2023/day02/input.txt").unwrap()));
        assert_eq!(79315, part_b(fs::read_to_string("input/2023/day02/input.txt").unwrap()));
    }
}