toj 1196 栈的运用（模拟浏览器）

两个栈来模拟浏览器的操作，简单模拟。

 1 #include <iostream>

 2 #include <string>

 3 #include <stack>

 4 using namespace std;

 5 

 6 stack<string> forward;

 7 stack<string> back;

 8 

 9 int main ()

10 {

11     string cur("http://www.acm.org/"), tmp;

12     while ( cin >> tmp )

13     {

14         if ( tmp == "QUIT" )

15         {

16             break;

17         }

18         else if ( tmp == "BACK" )

19         {

20             if ( back.empty() )

21             {

22                 cout << "Ignored" << endl;

23             }

24             else

25             {

26                 forward.push(cur);

27                 cur = back.top();

28                 back.pop();

29                 cout << cur << endl;

30             }

31         }

32         else if ( tmp == "FORWARD" )

33         {

34             if ( forward.empty() )

35             {

36                 cout << "Ignored" << endl;

37             }

38             else

39             {

40                 back.push(cur);

41                 cur = forward.top();

42                 forward.pop();

43                 cout << cur << endl;

44             }

45         }

46         else if ( tmp == "VISIT" )

47         {

48             back.push(cur);

49             cin >> cur;

50             while ( !forward.empty() )

51             {

52                 forward.pop();

53             }

54             cout << cur << endl;

55         }

56     }

57     return 0;

58 }