要注意pop_back和back()的区别
#include <bits/stdc++.h>
using namespace std;void Push(vector<int> &v,int x)
{v.push_back(x);
}void Top(vector<int> &v)
{if(!v.empty()){cout<<v.back()<<endl;// v.pop_back();}else {cout<<"error"<<endl;}
}void Pop(vector<int> &v)
{if(!v.empty()){cout<<v.back()<<endl;v.pop_back();}else {cout<<"error"<<endl;}
}
int main()
{int n;cin>>n;string s;vector<int>v;for(int i=0;i<=n;i++){getline(cin,s);if(s[0]=='p'&&s[1]=='u'&&s[2]=='s'&&s[3]=='h'){int value;value=stoi(s.substr(5));Push(v,value);}else if(s=="pop"){Pop(v);}else if(s=="top"){Top(v);}}return 0;
}
// 64 位输出请用 printf("%lld")
