zoukankan      html  css  js  c++  java
  • Discover the Web(栈模拟)

    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. You are asked to implement this. The commands are:

    1. BACK: If the backward stack is empty, the command is ignored. Otherwise, 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.
    2. FORWARD: If the forward stack is empty, the command is ignored. Otherwise, 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.
    3. VISIT <url>: 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.
    4. QUIT: Quit the browser.

    The browser initially loads the web page at the URL 'http://www.lightoj.com/'

    Input

    Input starts with an integer T (≤ 100), denoting the number of test cases.

    Each case contains some commands. The keywords BACK, FORWARD, VISIT, and QUIT are all in uppercase. URLs have no whitespace and have at most 50 characters. The end of case is indicated by the QUIT command and it shouldn't be processed. Each case contains at most 100 lines.

    Output

    For each case, print the case number first. For each command, print the URL of the current page (in a line) after the command is executed if the command is not ignored. Otherwise, print 'Ignored'.

    Sample Input

    1

    VISIT http://uva.onlinejudge.org/

    VISIT http://topcoder.com/

    BACK

    BACK

    BACK

    FORWARD

    VISIT http://acm.sgu.ru/

    BACK

    BACK

    FORWARD

    FORWARD

    FORWARD

    QUIT

    Sample Output

    Case 1:

    http://uva.onlinejudge.org/

    http://topcoder.com/

    http://uva.onlinejudge.org/

    http://www.lightoj.com/

    Ignored

    http://uva.onlinejudge.org/

    http://acm.sgu.ru/

    http://uva.onlinejudge.org/

    http://www.lightoj.com/

    http://uva.onlinejudge.org/

    http://acm.sgu.ru/

    Ignored

    题目意思:利用栈模拟一下浏览器访问网页的过程。

    解题思路:建立两个栈,分别储存向前和向后的元素,其实就是在来回倒。

    唉,好久没做题了,碰上这一道栈的题,来回做了好久,不过也是在补之前的漏洞,之前就碰到过这样一道双栈的题目,然而并没有及时补题,拖到了现在。

     1 #include<iostream>
     2 #include<stack>
     3 #include<algorithm>
     4 #include<stdio.h>
     5 using namespace std;
     6 int main()
     7 {
     8     int t,count=1;
     9     string x,y;
    10     scanf("%d",&t);
    11     while(t--)
    12     {
    13         printf("Case %d:
    ",count++);
    14         stack<string>s1;
    15         stack<string>s2;
    16         s1.push("http://www.lightoj.com/");
    17         while(1)
    18         {
    19             cin>>x;
    20             if(x[0]=='Q')
    21             {
    22                 break;
    23             }
    24             else if(x[0]=='V')
    25             {
    26                 cin>>y;
    27                 s1.push(y);
    28                 cout<<y<<endl;
    29                 while(!s2.empty())///清空
    30                 {
    31                     s2.pop();
    32                 }
    33             }
    34             else if(x[0]=='B')///因为s1栈顶元素是当前访问的页面,后退一步必须返回当前栈顶的下一个元素。
    35             {
    36                 if(s1.size()>1)///此时栈内必须有两个以上的元素
    37                 {
    38                     s2.push(s1.top());
    39                     s1.pop();///删掉当前的页面
    40                     cout<<s1.top()<<endl;
    41                 }
    42                 else
    43                 {
    44                     cout<<"Ignored"<<endl;
    45                 }
    46             }
    47             else if(x[0]=='F')
    48             {
    49                 if(!s2.empty())
    50                 {
    51                     s1.push(s2.top());
    52                     cout<<s2.top()<<endl;
    53                     s2.pop();///删掉当前的页面
    54                 }
    55                 else
    56                 {
    57                     cout<<"Ignored"<<endl;
    58                 }
    59             }
    60         }
    61     }
    62     return 0;
    63 }
  • 相关阅读:
    PPT能输英文不能输汉字
    常用HTML正则表达式
    Log4j使用总结
    JsonConfig过滤对象属性
    打开”我的电脑“,不显示”共享文档“和”我的文档“,解决办法。(windows XP系统)
    错误org.hibernate.LazyInitializationException
    Tomcat中实现IP访问限制
    windows server 2008中让AD域中的普通用户可以 远程登录 域控服务器。
    ibatis简介及 like查询
    IE访问页面的时候,受限制的解决方案。
  • 原文地址:https://www.cnblogs.com/wkfvawl/p/9085163.html
Copyright © 2011-2022 走看看