アルゴリズムと数学 041

https://atcoder.jp/contests/math-and-algorithm/tasks/math_and_algorithm_al

出勤時間と退勤時間をマージしてソートしておくと、そのあとは線形時間で時刻ごとの人数が得られます。

// Convenience Store 2
#![allow(non_snake_case)]


//////////////////// library ////////////////////

fn read<T: std::str::FromStr>() -> T {
    let mut line = String::new();
    std::io::stdin().read_line(&mut line).ok();
    line.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace()
            .map(|e| e.parse().ok().unwrap()).collect()
}


//////////////////// process ////////////////////

fn read_input() -> (usize, Vec<(usize, usize)>) {
    let T: usize = read();
    let N: usize = read();
    let intervals = (0..N).map(|_| read_vec()).map(|v| (v[0], v[1])).
                                    collect::<Vec<(usize, usize)>>();
    (T, intervals)
}

fn sort(intervals: Vec<(usize, usize)>) -> Vec<(usize, i32)> {
    let mut v = intervals.into_iter().
                        map(|(L, R)| vec![(L, 1), (R, -1)]).
                        flatten().collect::<Vec<(usize, i32)>>();
    v.sort();
    v
}

fn f(T: usize, intervals: Vec<(usize, usize)>) {
    let moves = sort(intervals);
    let mut num_workers: i32 = 0;
    let mut i = 0;
    for t in 0..T {
        while i < moves.len() && t == moves[i].0 {
            num_workers += moves[i].1;
            i += 1
        }
        println!("{}", num_workers)
    }
}

fn main() {
    let (T, intervals) = read_input();
    f(T, intervals)
}