题解 | #【模板】队列#

#include <iostream>
#include <queue>
#include <stack>
using namespace std;

int main() {
    int n;
    int num;
    queue<int> que;
    string operation;
    cin >> n;
    while (n--) {
        cin >> operation;
        if (operation == "push") {
            cin >> num;
            que.push(num);
        } else if (operation == "front") {
            if (que.empty()) {
                cout << "error" << endl;
            } else {
                cout << que.front() << endl;
            }
        } else if (operation == "pop") {
            if (que.empty()) {
                cout << "error" << endl;
            } else {
                cout << que.front() << endl;
                que.pop();
            }
        }
    }
    return 0;
}
// 64 位输出请用 printf("%lld")