1028 Web Navigation

两个栈

#include<iostream>#include<string>#include<stack>using namespace std; int main(){freopen("input.txt","r",stdin);freopen("output3.txt","w",stdout);stack<string>sb,sf;string in;string out;sb.push("http://www.acm.org/");while(cin>>in){if(in=="VISIT"){cin>>out;sb.push(out);cout<<out<<endl;while(!sf.empty()){sf.pop();}}if(in=="BACK"){if(sb.size()>1){sf.push(sb.top());sb.pop();cout<<sb.top()<<endl;}else{cout<<"Ignored"<<endl;}}if(in=="FORWARD"){if(!sf.empty()){sb.push(sf.top());cout<<sf.top()<<endl;sf.pop();}else{cout<<"Ignored"<<endl;}}if(in=="QUIT"){break;}}    return 0;}