题解 | 删除区间

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<int[]> list = new ArrayList<>();
        while (n-- > 0) {
            int a = sc.nextInt(), b = sc.nextInt();
            list.add(new int[] {a, b});
        }
        list.sort((a, b) -> a[1] - b[1]);
        int right = Integer.MIN_VALUE, ans = 0;
        for (int[] num : list) {
            if (right != Integer.MIN_VALUE && num[0] <= right) ans++;
            else right = num[1];
        }
        System.out.println(ans);
        sc.close();
    }
}