PKU_1028

 

题目链接：http://acm.pku.edu.cn/JudgeOnline/problem?id=1028

 

弄2个栈进行操作即可，注意在输入 VISIT时 forward stack 要清空。

 

#include <iostream>#include <stack>#include <string>using namespace std;int main(){stack<string> back,forward;string str,s;while(cin>>str&&str!="QUIT"){if(back.empty()) back.push("http://www.acm.org/");if(str=="VISIT"){cin>>s;cout<<s<<endl;back.push(s);while(!forward.empty())forward.pop();}else if(str=="BACK"){if(back.size()>1)forward.push(back.top());back.pop();if(back.empty())cout<<"Ignored"<<endl;else cout<<back.top()<<endl;}else if(str=="FORWARD"){if(forward.empty())cout<<"Ignored"<<endl;else {cout<<forward.top()<<endl;back.push(forward.top());forward.pop();}}}return 0;}