C++ 代码

# include <iostream>
using namespace std;
const int N = 100010;

int q[N], hh = 0, tt = -1;    
void push(int x)
{
    q[ ++tt ] = x;
}

void pop ()
{
    hh ++;
}

string empty()
{
    if (tt >= hh) return "NO";
    else return "YES";
}

int query()
{
    return q[hh];
}

int main()
{
    int m;
    cin >> m;
    while (m --)
    {
        string op;
        cin >> op;
        if (op == "push")
        {
            int x;
            cin >> x;
            push(x);

        }
        else if (op == "pop")
        {
            pop();
        }

        else if (op == "empty")
        {
            string ans1;
            ans1 = empty();
            cout << ans1 << endl;
        }

        else if (op == "query")
        {
            int ans2;
            ans2 = query();
            cout << ans2 << endl;
        }
    }
    return 0;

}