fn p1(v: &[(u64, u64)]) -> u64 {
    v.iter().fold(0, |h, &(low, high)| {
        if low > h {
            return h;
        }
        std::cmp::max(h, high + 1)
    })
}

fn p2(v: &[(u64, u64)]) -> u64 {
    v.iter()
        .chain(std::iter::once(&(1 << 32, 1 << 32)))
        .fold((0, 0), |(h, c), &(low, high)| if low > h {
            (high + 1, c + low - h)
        } else {
            (std::cmp::max(h, high + 1), c)
        })
        .1
}

fn main() {
    let mut pairs: Vec<_> = include_str!("../../20.input")
        .lines()
        .map(|line| {
            let v: Vec<_> = line.split('-').map(|w| w.parse::<u64>().unwrap()).collect();
            (v[0], v[1])
        })
        .collect();
    pairs.sort();
    println!("P1 = {}", p1(&pairs));
    println!("P2 = {}", p2(&pairs));
}