题解 | #剩下的树#Vector/Iterator用法

#include <cstdio>
#include<iostream>
#include<vector>
using namespace std;
int main() {
    int L, M;
    scanf("%d%d", &L, &M);
    vector<int> vec(L+1); //0~L vector vec(0)有树 vec(1)无树
    for (int i = 0; i < M; ++i) {
        int left, right;
        scanf("%d%d", &left, &right);
        for (int j = left; j <= right; ++j) {
            vec[j] = 1;
        }
    }
    int treenum;
    vector<int>::iterator it;
    for (it = vec.begin(); it != vec.end(); ++it) {
        if (*it == 0) treenum++;
    }
    printf("%d", treenum);
    return 0;
}