题解 | #剩下的树#

#include<cstdio>

int main() {
    int tree[10001];
    int L, M ;
    scanf("%d%d", &L, &M);
    for (int i = 0; i <= L; ++i) {
        tree[i] = 1;
    }
    for (int idx = 0; idx < M; ++idx) { //外部循环可以用无关字母
        int left, right;
        scanf("%d%d", &left, &right);
        for (int i = left; i <= right; ++i) {
            tree[i] = 0;
        }
    }

    int rem = 0;
    for (int i = 0; i <= L; ++i) {
        if (tree[i] == 1) {
            ++rem;
        }

    }
    printf("%d\n", rem);
}