题解 | 剩下的树

#include <iostream>
#include <vector>
using namespace std;

int main() {
    int L, M;
    cin >> L >> M;
    vector<bool> road(L + 1);
    for (int i = 0; i <= L; i++)   road[i] = true;
    int left, right;
    while (M--) {
        cin >> left >> right;
        for (int i = left; i <= right; i++)    road[i] = false;
    }
    int count = 0;
    for (int i = 0; i <= L; i++) {
        if (road[i]) {
            count++;
        }
    }
    cout << count << endl;
}
// 64 位输出请用 printf("%lld")

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