C++ 代码：计算马路上剩余的树木数量

#include <iostream>
#include <vector>

using namespace std;

int main() {
    int L, M;
    cin >> L >> M;
    
    vector<bool> trees(L + 1, true);
    for (int i = 0; i < M; i++) {
        int start, end;
        cin >> start >> end;
        
        for (int j = start; j <= end; j++) {
            trees[j] = false;
        }
    }
    
    int count = 0;
    for (int i = 0; i <= L; i++) {
        if (trees[i]) {
            count++;
        }
    }
    
    cout << count << endl;
    
    return 0;
}