https://atcoder.jp/contests/math-and-algorithm/tasks/math_and_algorithm_bn
終了時刻でソートすればよいです。
// Interval Scheduling Problem #![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() -> Vec<(i32, i32)> { let N: usize = read(); let intervals: Vec<(i32, i32)> = (0..N).map(|_| read_vec()). map(|v| (v[0], v[1])).collect(); intervals } fn f(mut intervals: Vec<(i32, i32)>) -> i32 { intervals.sort_by_key(|i| i.1); let mut counter: i32 = 0; let mut last: i32 = 0; for (start, end) in intervals.into_iter() { if start >= last { counter += 1; last = end } } counter } fn main() { let intervals = read_input(); println!("{}", f(intervals)) }