题解 | #剩下的树#

#include <stdio.h>
#include<stdlib.h>
int main() {
    int L, c;
    scanf("%d %d", &L, &c);
    int* arr = (int*)calloc(L + 1, sizeof(int));
    while (c--) { // 注意 while 处理多个 case
        int low, high;
        scanf("%d %d", &low, &high);
        for (int i = low; i <= high; ++i) {
            arr[i] = 1;
        }
    }
    int cnt = 0;
    for (int i = 1; i <= L; ++i) {
        if (arr[i] == 0) {
            ++cnt;
        }
    }
    printf("%d", cnt + 1);
    return 0;
}