day02.rs

use std::collections::HashSet;

use aoc_core::prelude::*;

fn part1(input: &Input) -> isize {
    input.lines()
        .map(|x| x.integers().collect::<Vec<_>>())
        .filter(|x| is_safe(x))
        .count()
        .try_into()
        .unwrap()
}

fn part2(input: &Input) -> isize {
    input.lines()
        .map(|x| x.integers().collect::<Vec<_>>())
        .filter(|x| {
            (0..x.len()).any(|i| {
                let mut new_values = x.clone();
                new_values.remove(i);

                is_safe(&new_values)
            })
        })
        .count()
        .try_into()
        .unwrap()
}

fn is_safe(levels: &[isize]) -> bool {
    let diff = levels
        .windows(2)
        .map(|x| x[0] - x[1]);

    diff.clone().map(isize::signum).collect::<HashSet<isize>>().len() == 1 &&
    diff.clone().all(|x| x.abs() <= 3)
}

runner!();

#[cfg(test)]
#[test]
fn test() {
    let input = Input::new("
        7 6 4 2 1
        1 2 7 8 9
        9 7 6 2 1
        1 3 2 4 5
        8 6 4 4 1
        1 3 6 7 9
    ".to_string());

    assert_eq!(part1(&input), 2, "Part 1");
    assert_eq!(part2(&input), 4, "Part 2");
}