Java实现 洛谷 P1047 [NOIP2005 普及组] 校门外的树

import java.util.Scanner;

public class 校门外的树 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        boolean[] l = new boolean[sc.nextInt()+1];//501棵树
        int m = sc.nextInt(), ans = 0;
        for (int i=0;i<l.length;i++) {
            l[i] = true;
        }
        for(int i=1;i<=m;i++){
            int start = sc.nextInt(), end = sc.nextInt();
            for(int j = start; j <= end; j++)
                l[j] = false;
        }
        for(int i = 0; i < l.length; i++) {//从前到后遍历，区间为true的，ans++
            if (l[i] == true) {
                ans++;
            }
        }
        System.out.println(ans);
    }
}