最最简单的题解！！！！！！！！！！！！！

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin>>n;
    while(n--){
        stack<int>a;
        string s;
        cin>>s;
        if(s=="empty"){
            if(a.empty()==1){
                cout<<"yes"<<endl;
            }else{
                cout<<"no"<<endl;
            }
        }else if(s=="push"){
            int x;
            cin>>x;
            a.push(x);
        }else if(s=="size"){
            cout<<"size = "<<a.size()<<endl;
        }else if(s=="top"){
            if(a.empty()==0){
                cout<<"top = "<<a.top()<<endl;
            }else{
                cout<<"top fail"<<endl;
            }
        }else if(s=="pop"){
            if(a.empty()==0){
                int f=a.top();
                a.pop();
                cout<<"pop "<<f<<endl;
            }else{
                cout<<"pop fail"<<endl;
            }
        }
    }
    return 0;
}

点个赞吧，就当积德了