C++ 代码

#include <iostream>
using namespace std;
const int N = 100010;
int q[N];
int tail,head;

int main(){
    int n;
    cin >> n;
    while(n--){
        string op;
        cin >> op;
        int x;
        if(op == "push"){
            cin >> x;
            q[tail++] = x;
        }else if(op == "pop"){
            ++head;
        }
        else if(op == "empty"){
            cout << ( (head == tail ? "YES" : "NO") ) << endl;
        }else{
            cout << q[head] << endl;
        }
    }
    return 0;
}