advent-of-code-2024/d2/d2p1.rs

use advent_of_code_2024::{make_main, SResult};

make_main!();

// CODE

#[derive(PartialEq)]
enum Direction {
    Up,
    Down,
}

impl Direction {
    fn from(a: usize, b: usize) -> Self {
        if a > b {
            Direction::Down
        } else {
            Direction::Up
        }
    }
}

fn solve(lines: Vec<String>) -> SResult<usize> {
    let mut failed = 0;
    for line in lines.iter() {
        let reports: Vec<usize> = line.split_whitespace().map(|v| v.parse::<usize>().unwrap()).collect();
        let mut i = 0;
        let direction = Direction::from(reports[0], reports[1]);
        while i + 1 < reports.len() {
            let delta = reports[i].abs_diff(reports[i+1]);
            if delta < 1 || delta > 3 {
                failed += 1;
                break;
            }
            if direction != Direction::from(reports[i], reports[i+1]) {
                failed += 1;
                break;
            }
            i += 1;
        }
    }
    Ok(lines.len() - failed)
}

// CODE

#[cfg(test)]
mod tests {
    use advent_of_code_2024::input;

    use super::*;
    #[test]
    fn sample_input() {
        let strings: Vec<String> = input!("d2p1.txt");
        let got = solve(strings).unwrap();
        assert_eq!(got, 2);
    }
}