advent-of-code/2023/rust/src/day2.rs

use std::cmp::{max, min};

use crate::prelude::*;

extern crate nom;

mod prelude;

use nom::{
    branch::alt,
    bytes::complete::{tag, take_while_m_n},
    combinator::{map_res, value},
    multi::separated_list0,
    IResult,
};

fn main() {
    Day2::show(day_input(2), day_input(2))
}

type Solution = usize;

#[derive(Debug, PartialEq, Clone)]
enum Reveal {
    Red(usize),
    Green(usize),
    Blue(usize),
}

#[derive(Debug, PartialEq)]
struct RevealGroup {
    red: Option<usize>,
    green: Option<usize>,
    blue: Option<usize>,
}

impl RevealGroup {
    fn power(&self) -> usize {
        println!("reveal group power for {:?}", self);
        self.red.unwrap_or(0) * self.green.unwrap_or(0) * self.blue.unwrap_or(0)
    }
}

impl From<Vec<Reveal>> for RevealGroup {
    fn from(value: Vec<Reveal>) -> Self {
        // TODO: this obviously won't work if the vector contains multiple reveals of the same kind
        // there's probably a simpler way to parse it out
        let mut result = Self {
            red: None,
            blue: None,
            green: None,
        };
        for v in value {
            match v {
                Reveal::Red(v) => result.red = Some(v),
                Reveal::Green(v) => result.green = Some(v),
                Reveal::Blue(v) => result.blue = Some(v),
            }
        }
        result
    }
}

#[derive(Debug, PartialEq)]
struct Game {
    id: usize,
    reveal_groups: Vec<RevealGroup>,
}

impl Game {
    fn made_possible(&self) -> RevealGroup {
        let mut red = 0;
        let mut green = 0;
        let mut blue = 0;
        for rg in &self.reveal_groups {
            red = max(rg.red.unwrap_or(0), red);
            green = max(rg.green.unwrap_or(0), green);
            blue = max(rg.blue.unwrap_or(0), blue);
        }
        RevealGroup {
            red: Some(red),
            green: Some(green),
            blue: Some(blue),
        }
    }
}

fn int(input: &str) -> IResult<&str, usize> {
    map_res(take_while_m_n(1, 16, |c: char| c.is_numeric()), |s| {
        usize::from_str_radix(s, 10)
    })(input)
}

fn reveal(input: &str) -> IResult<&str, Reveal> {
    let (input, num) = int(input)?;
    alt((
        value(Reveal::Red(num), tag(" red")),
        value(Reveal::Green(num), tag(" green")),
        value(Reveal::Blue(num), tag(" blue")),
    ))(input)
}

fn reveal_group(input: &str) -> IResult<&str, RevealGroup> {
    let (input, reveals) = separated_list0(tag(", "), reveal)(input)?;
    Ok((input, RevealGroup::from(reveals)))
}

fn game(input: &str) -> IResult<&str, Game> {
    let (input, id) = int(tag("Game ")(input)?.0)?;
    let (input, reveal_groups) = separated_list0(tag("; "), reveal_group)(tag(": ")(input)?.0)?;

    Ok((input, Game { id, reveal_groups }))
}

struct Day2 {}
impl Day2 {}

impl AoCSolution for Day2 {
    type Input = String;
    type Solution = Solution;

    fn part1(input: Self::Input) -> Self::Solution {
        const MAX_RED: Solution = 12;
        const MAX_GREEN: Solution = 13;
        const MAX_BLUE: Solution = 14;

        let valid_reveal_group = |rg: &RevealGroup| {
            rg.red.unwrap_or(0) <= MAX_RED
                && rg.green.unwrap_or(0) <= MAX_GREEN
                && rg.blue.unwrap_or(0) <= MAX_BLUE
        };

        input
            .lines()
            .map(|s| game(s).unwrap().1)
            .filter(|g| g.reveal_groups.iter().all(valid_reveal_group))
            .map(|g| g.id)
            .sum()
    }

    fn part2(input: Self::Input) -> Self::Solution {
        input
            .lines()
            .map(|s| game(s).unwrap().1.made_possible().power())
            .sum()
    }
}

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

    #[test]
    fn test() {
        assert_eq!(
            Day2::part1(
                r#"Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green
Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green"#
                    .into()
            ),
            8
        );
        assert_eq!(
            Day2::part2(
                r#"Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green
Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green"#
                    .into()
            ),
            2286
        );
    }
}