题解 | #【模板】队列#

#include <iostream>
#include <queue>

using namespace std;

int main() {
    int n;
    cin >> n;
    queue<int> que;
    string s;
    int num;
    for (int i = 0; i < n; i++) {
        cin >> s;
        if (s == "push") {
            cin >> num;
            que.push(num);
        }
        if (s == "pop") {
            if (que.empty())
                cout << "error" << endl;
            else {
                cout << que.front() << endl;
                que.pop();
            }
        }
        if (s == "front") {
            if (que.empty())
                cout << "error" << endl;
            else
                cout << que.front() << endl;
        }
    }
    return 0;
}