题解 | 剩下的树

#include<stdio.h>
#include<vector>
using namespace std;

int main() {
    int L, M;   //树的总数量L，区间的个数M
    int count = 0;
    scanf("%d%d", &L, & M);
    vector<int> tree(L + 1, 0); //0表示该点有树，1表示无树
    for (int i = 0; i < M; i++) {
        int left, right;
        scanf("%d%d", &left, &right);
        for (int j = left; j <= right; j++) {
            tree[j] = 1;
        }
    }
    vector<int>::iterator it;
    for (it = tree.begin(); it != tree.end(); it++) {
        if (*it == 0) {
            count++;
        }
    }
    printf("%d", count);
}