数组模拟队列

#include <iostream>

using namespace std;

const int N = 1e6 + 10;

int q[N], hh, tt = -1;      //hh表示队头，tt表示队尾

int main() 
{
    int m;
    cin >> m;

    while (m -- ) 
    {
        string op;
        int x;

        cin >> op;

        if (op == "push") 
        {
            cin >> x;
            q[ ++ tt] = x;
        } 
        else if (op == "pop") hh ++ ;
        else if (op == "query") printf("%d\n", q[hh]);
        else 
        {
            if (hh > tt) printf("YES\n");
            else printf("NO\n");
        }
    }

    return 0;
}