C++ 代码

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

int stk[N], tt = 0;

void push(int x)
{
    stk[ ++tt ] = x;

}

void pop ()
{
    tt --;
}

string empty()
{
    if (tt > 0)
    return "NO";
    else
    return "YES";
}

int query()
{
    return stk[tt];
}

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

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

        else if (op == "empty")
        {
            string ans1;
            ans1 = empty();
            // printf(ans1);
            cout << ans1 << endl;
        }
        else if (op == "query")
        {
            int ans2;
            ans2 = query();
            // printf(ans2);
            cout << ans2 << endl;
        }

    }
}