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http://poj.org/problem?id=1028
1
2
3
4 /* ***********************************************
5 Author :111qqz
6 Created Time :2016年02月19日 星期五 15时45分01秒
7 File Name :1028.cpp
8 ************************************************ */
9
10 #include <algorithm>
11 #include <cstdio>
12 #include <iostream>
13 #include <cstring>
14 #include <string>
15 #include <cmath>
16 #include <map>
17 #include <stack>
18 #include <queue>
19
20 using namespace std;
21 typedef long long LL;
22 const int inf = 8E8;
23 stack<string> backstack;
24 stack<string> forwardstack;
25 string cur;
26 string cmd;
27 int main()
28 {
29 cur ="http://www.acm.org/";
30
31 while (cin>>cmd)
32 {
33 if (cmd=="QUIT")
34 {
35 break;
36 }
37 if (cmd=="BACK")
38 {
39 if (backstack.empty())
40 {
41 cout<<"Ignored"<<endl;
42 continue;
43 }
44 forwardstack.push(cur);
45 cur=backstack.top();
46 backstack.pop();
47 cout<<cur<<endl;
48 }
49 if (cmd=="FORWARD")
50 {
51 if (forwardstack.empty())
52 {
53 cout<<"Ignored"<<endl;
54 continue;
55 }
56 backstack.push(cur);
57 cur=forwardstack.top();
58 forwardstack.pop();
59 cout<<cur<<endl;
60 }
61 if (cmd=="VISIT")
62 {
63 backstack.push(cur);
64
65 cin>>cur;
66 while (!forwardstack.empty()) forwardstack.pop();
67 cout<<cur<<endl;
68
69 }
70 }
71
72
73 return 0;
74 }