题解 | #剩下的树#

#include <stdio.h>

int main() {
    int l, m;
    int list1[10001];
    scanf("%d %d", &l, &m);
    for (int j = 0 ; j <= l; j++) {
        list1[j] = 1;
    }
    for (int i = 0; i < m; i++) {
        int from, to;
        scanf("%d %d", &from, &to);
        for (int k = from; k <= to; k++) {
            list1[k] = 0;
        }
    }
    int treenum = 0;
    for (int i = 0; i <= l; i++) {
        if (list1[i] == 1) {
            treenum++;
        }
    }
    printf("%d", treenum);
    return 0 ;
}