题解 | 【模板】栈的操作

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main()
{
    ll t;
    cin>>t;
    stack<ll>z;
    while(t--)
    {

        string s;
        cin>>s;
        if(s=="push"){
            int x;
            cin>>x;
            z.push(x);
        }
        else if(s=="size"){
            cout<<z.size()<<endl;
        }
        else if(s=="pop"){
            if(z.empty()){
                cout<<"Empty"<<endl;
            }
            else z.pop();
        }
        else if(s=="query")
            {
            if(z.empty()){
                cout<<"Empty"<<endl;
            }
            else cout<<z.top()<<endl;

            
            }
    }
    return 0;
}