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 1 Source Code
 2 
 3 Problem: 1028        User: 13408100238
 4 Memory: 200K        Time: 0MS
 5 Language: C++        Result: Accepted
 6 Source Code
 7 #include"iostream"
 8 #include"cstring"
 9 #include"string"
10 #include"stack"
11 using namespace std;
12 int main()
13 {
14     stack<string> s1,s2;
15     string s,ss;
16     s="http://www.acm.org/";
17     s1.push(s);
18     while(cin>>s)
19     {
20         if(s=="QUIT")
21            break;
22         if(s=="VISIT")
23         {
24             cin>>ss;
25             cout<<ss<<endl;
26             s1.push(ss);
27             while(!s2.empty())
28                s2.pop();
29         }
30         else if(s=="BACK")
31         {
32             //cout<<"back  "<<s1.size()<<endl;
33             if(s1.size()>=2)
34             {
35                 s2.push(s1.top());
36                 s1.pop();
37                 cout<<s1.top()<<endl;
38             }
39             else
40                cout<<"Ignored"<<endl;
41         }
42         else if(s=="FORWARD")
43         {
44             if(!s2.empty())
45             {
46                 cout<<s2.top()<<endl;
47                 s1.push(s2.top());
48                 s2.pop();
49             }
50             else 
51               cout<<"Ignored"<<endl;
52         }
53     }
54     return 0;
55 }