PKU 1024 Web Navigation 解法及教训总结

此道题就是考查基本数据结构堆栈的操作，之所以要在此写一下 ，是要总结一下做题的教训。以提醒自己少犯类似的错误。之所以这个简单的问题耗费了我一上午的时间，居然是因为我没有认真读题，只能说有点杯具了。:-(

 

代码

   
     

    
      
    
       1 
    
      下面把代码贴出来，写的不好，别喷我。:
    
      -
    
      )

    
       2 
    
      #include 
    
      <
    
      iostream
    
      >
    
      

    
       3 
    
       
    
      using
    
       
    
      namespace
    
       std;

    
       4 
    
      class
    
       Stack 

    
       5 
    
      {

    
       6 
    
      public
    
      :

    
       7 
    
       
    
      void
    
       PushBack (
    
      char
    
       url[]);

    
       8 
    
       
    
      void
    
       PopUp (
    
      char
    
       url[]);

    
       9 
    
       inline 
    
      bool
    
       IsEmpty (
    
      void
    
      ) {
    
      return
    
       top 
    
      ==
    
       
    
      -
    
      1
    
      ;}

    
      10 
    
       inline 
    
      bool
    
       IsFull (
    
      void
    
      ) {
    
      return
    
       top 
    
      ==
    
       
    
      100
    
      ;}

    
      11 
    
       
    
      int
    
       Top(){
    
      return
    
       top;}

    
      12 
    
       inline 
    
      void
    
       Reset (
    
      void
    
      ){top 
    
      =
    
       
    
      -
    
      1
    
      ;}

    
      13 
    
       inline 
    
      void
    
       Print (
    
      void
    
      ) 

    
      14 
    
       {

    
      15 
    
       cout
    
      <<
    
      Url[top]
    
      <<
    
      endl;

    
      16 
    
       }

    
      17 
    
       Stack ();

    
      18 
    
       
    
      ~
    
      Stack ();

    
      19 
    
      private
    
      :

    
      20 
    
       
    
      char
    
       Url[
    
      101
    
      ][
    
      71
    
      ];

    
      21 
    
       
    
      int
    
       top;

    
      22 
    
      };

    
      23 
    
      

    
      24 
    
      Stack::
    
      ~
    
      Stack()

    
      25 
    
      {

    
      26 
    
      }

    
      27 
    
      Stack::Stack ()

    
      28 
    
      {

    
      29 
    
       top 
    
      =
    
       
    
      -
    
      1
    
      ;

    
      30 
    
      }

    
      31 
    
      

    
      32 
    
      void
    
       Stack::PushBack (
    
      char
    
       url[])

    
      33 
    
      {

    
      34 
    
       
    
      if
    
       (IsFull())

    
      35 
    
       
    
      return
    
      ;

    
      36 
    
       
    
      ++
    
       top;

    
      37 
    
       strcpy(Url[top], url);

    
      38 
    
      }

    
      39 
    
      

    
      40 
    
      void
    
       Stack::PopUp (
    
      char
    
       url[])

    
      41 
    
      {

    
      42 
    
       
    
      if
    
       (IsEmpty())

    
      43 
    
       {

    
      44 
    
       strcpy (url, 
    
      ""
    
      );

    
      45 
    
       
    
      return
    
      ;

    
      46 
    
       }

    
      47 
    
       strcpy (url, Url[top]);

    
      48 
    
       
    
      --
    
       top;

    
      49 
    
      }

    
      50 
    
      

    
      51 
    
      int
    
       main ()

    
      52 
    
      {

    
      53 
    
       Stack backward, forward;

    
      54 
    
       
    
      char
    
       command[
    
      10
    
      ];

    
      55 
    
       
    
      char
    
       url[
    
      71
    
      ] 
    
      =
    
       
    
      "
    
      http://www.acm.org/
    
      "
    
      ;

    
      56 
    
       cin
    
      >>
    
      command;

    
      57 
    
       
    
      while
    
       (strcmp (command, 
    
      "
    
      QUIT
    
      "
    
      ) 
    
      !=
    
       
    
      0
    
      )

    
      58 
    
       {

    
      59 
    
       
    
      if
    
       (strcmp (command, 
    
      "
    
      VISIT
    
      "
    
      ) 
    
      ==
    
       
    
      0
    
      )

    
      60 
    
       { 

    
      61 
    
       backward.PushBack(url);

    
      62 
    
       cin
    
      >>
    
      url;

    
      63 
    
       cout
    
      <<
    
      url
    
      <<
    
      endl;

    
      64 
    
       forward.Reset();

    
      65 
    
       }

    
      66 
    
       
    
      else
    
       
    
      if
    
       (strcmp (command, 
    
      "
    
      BACK
    
      "
    
      ) 
    
      ==
    
       
    
      0
    
      )

    
      67 
    
       {

    
      68 
    
       
    
      if
    
       (backward.IsEmpty())

    
      69 
    
       {

    
      70 
    
       cout
    
      <<
    
      "
    
      Ignored
    
      "
    
      <<
    
      endl;

    
      71 
    
       
    
      goto
    
       input;

    
      72 
    
       }

    
      73 
    
       forward.PushBack(url);

    
      74 
    
       backward.PopUp(url);

    
      75 
    
       cout
    
      <<
    
      url
    
      <<
    
      endl;

    
      76 
    
      

    
      77 
    
       }

    
      78 
    
       
    
      else
    
       
    
      if
    
       (strcmp (command, 
    
      "
    
      FORWARD
    
      "
    
      ) 
    
      ==
    
       
    
      0
    
      )

    
      79 
    
       {

    
      80 
    
       
    
      if
    
       (forward.IsEmpty())

    
      81 
    
       {

    
      82 
    
       cout
    
      <<
    
      "
    
      Ignored
    
      "
    
      <<
    
      endl;

    
      83 
    
       
    
      goto
    
       input;

    
      84 
    
       }

    
      85 
    
       backward.PushBack(url);

    
      86 
    
       forward.PopUp(url);

    
      87 
    
       cout
    
      <<
    
      url
    
      <<
    
      endl;

    
      88 
    
       }

    
      89 
    
      input: cin
    
      >>
    
      command;

    
      90 
    
       }

    
      91 
    
       
    
      return
    
       
    
      0
    
      ;

    
      92 
    
      }
   
     

 

 

当然你也可以用stl中的stack那样更简单，代码更少。

最后总结一下教训吧，一定要认真读题。要不到时候真的是欲哭无泪啊。