校门外的树 （Java代码）

解题思路:





注意事项:





参考代码:

import java.util.Scanner;

public class 种树 {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int a = sc.nextInt();

a += 1;

int b = sc.nextInt();

int c, d;

int sum = 0;

int arr[] = new int[a];

for (int i = 0; i < a; i++)

arr[i] = 1;

for (int i = 0; i < b; i++) {

c = sc.nextInt();

d = sc.nextInt();

for (int x = 0; x < a; x++) {

if (x <= d && x >= c)

arr[x] = 0;

}

}

for (int x = 0; x < a; x++) {

if (arr[x] == 1)

sum++;

}

System.out.print(sum);

}

}