zoukankan      html  css  js  c++  java
  • ZOJ1061-Web Navigation

    Web Navigation

    Description

    Standard web browsers contain features to move backward and forward among the pages recently visited. One way to implement these features is to use two stacks to keep track of the pages that can be reached by moving backward and forward. In this problem, you are asked to implement this.
    The following commands need to be supported:
    BACK: Push the current page on the top of the forward stack. Pop the page from the top of the backward stack, making it the new current page. If the backward stack is empty, the command is ignored.
    FORWARD: Push the current page on the top of the backward stack. Pop the page from the top of the forward stack, making it the new current page. If the forward stack is empty, the command is ignored.
    VISIT : Push the current page on the top of the backward stack, and make the URL specified the new current page. The forward stack is emptied.
    QUIT: Quit the browser.
    Assume that the browser initially loads the web page at the URL http://www.acm.org/

    Input

    Input is a sequence of commands. The command keywords BACK, FORWARD, VISIT, and QUIT are all in uppercase. URLs have no whitespace and have at most 70 characters. You may assume that no problem instance requires more than 100 elements in each stack at any time. The end of input is indicated by the QUIT command.

    Output

    For each command other than QUIT, print the URL of the current page after the command is executed if the command is not ignored. Otherwise, print "Ignored". The output for each command should be printed on its own line. No output is produced for the QUIT command.

    Sample Input

    VISIT http://acm.ashland.edu/
    VISIT http://acm.baylor.edu/acmicpc/
    BACK
    BACK
    BACK
    FORWARD
    VISIT http://www.ibm.com/
    BACK
    BACK
    FORWARD
    FORWARD
    FORWARD
    QUIT

    Sample Output

    http://acm.ashland.edu/
    http://acm.baylor.edu/acmicpc/
    http://acm.ashland.edu/
    http://www.acm.org/
    Ignored
    http://acm.ashland.edu/
    http://www.ibm.com/
    http://acm.ashland.edu/
    http://www.acm.org/
    http://acm.ashland.edu/
    http://www.ibm.com/
    Ignored

     1 #include<cstdio>
     2 #include<iostream>
     3 #include<string>
     4 #include<stack>
     5 using namespace std;
     6  
     7 int main()
     8 {
     9     stack<string> back,forward;
    10     string now,URL;
    11     back.push("http://www.acm.org/");
    12     while(cin>>now)
    13     {
    14         if(now[0]=='Q')
    15             break;
    16         else if(now[0]=='V')
    17         {
    18             cin>>URL;
    19             back.push(URL);
    20             cout<<URL<<endl;
    21             while(!forward.empty())     
    22                 forward.pop();
    23         }
    24         else if(now[0]=='B')
    25         {
    26             if(back.size()>1)          
    27             {                        
    28                 forward.push(back.top());             
    29                 back.pop();
    30                 cout<<back.top()<<endl;
    31             }
    32             else
    33                 cout<<"Ignored"<<endl;
    34         }
    35         else
    36         {
    37             if(!forward.empty())
    38             {  
    39                 back.push(forward.top());
    40                 cout<<forward.top()<<endl;
    41                 forward.pop();
    42             }
    43             else
    44                 cout<<"Ignored"<<endl;
    45         }
    46     }
    47     return 0;
    48 }
  • 相关阅读:
    c语言|博客作业05
    C语言I博客作业04
    C语言II博客作业04
    C语言II博客作业03
    C语言II博客作业02
    C语言II博客作业01
    学期总结
    我的第一周C语言作业
    C语言I博客作业08
    C语言I博客作业07
  • 原文地址:https://www.cnblogs.com/youdiankun/p/3633026.html
Copyright © 2011-2022 走看看