题解 | 校门外的树

#include <stdio.h>

int main() {
    int L = 0;
    int M = 0;
    int length[100000] = { 0 };
    scanf("%d %d", &L, &M);
    while (M--) {
        int l = 0;
        int r = 0;
        int i = 0;
        scanf("%d %d", &l, &r);
        for (i = l; i <= r; i++) {
            length[i] = 1;
        }
    }
    int i = 0;
    int count = 0;
    for (i = 0; i <= L; i++) {
        if (length[i] == 0) {
            count++;
        }
    }
    printf("%d\n", count);
    return 0;
}