字典树

 

 

HDU 1251

代码

   
     

    
      
    
      #include
    
      <
    
      iostream
    
      >
    
      

    
      using
    
       
    
      namespace
    
       std;


    
      const
    
       
    
      int
    
       kind
    
      =
    
      26
    
      ;
    
      //
    
      字母种类
    
      

    
      

    
      struct
    
       Treenode
    
      //
    
      树的结点结构
    
      

    
      {
 
    
      int
    
       count;
    
      //
    
      这个附加变量在本题中记录遍历到该结点形成的字符串出现的次数，在不同题中可记录不同的内容。
    
      

    
       Treenode 
    
      *
    
      next[kind];
    
      //
    
      指向儿子结点
    
      

    
       Treenode()
    
      //
    
      每个结点的初始化
    
      

    
       {
 count
    
      =
    
      1
    
      ;
 
    
      for
    
      (
    
      int
    
       i
    
      =
    
      0
    
      ;i
    
      <
    
      kind;i
    
      ++
    
      )
 next[i]
    
      =
    
      NULL;
 }
};


    
      void
    
       insert(Treenode 
    
      *&
    
      root,
    
      char
    
       
    
      *
    
      word)
    
      //
    
      向以root为根结点的树中插入串word
    
      

    
      {
 Treenode 
    
      *
    
      location
    
      =
    
      root;
 
    
      int
    
       i
    
      =
    
      0
    
      ,branch
    
      =
    
      0
    
      ;
 
 
    
      if
    
      (location
    
      ==
    
      NULL) {location
    
      =
    
      new
    
       Treenode();root
    
      =
    
      location;}

 
    
      while
    
      (word[i])
 {
 branch
    
      =
    
      word[i]
    
      -
    
      '
    
      a
    
      '
    
      ;
 
    
      if
    
      (location
    
      ->
    
      next[branch]) location
    
      ->
    
      next[branch]
    
      ->
    
      count
    
      ++
    
      ;
    
      //
    
      如果该字符存在，串数量加1
    
      

    
       
    
      else
    
       location
    
      ->
    
      next[branch]
    
      =
    
      new
    
       Treenode();
    
      //
    
      如果不存在，建新结点
    
      

    
       i
    
      ++
    
      ;
 location
    
      =
    
      location
    
      ->
    
      next[branch];
 }
}


    
      int
    
       search(Treenode 
    
      *
    
      root,
    
      char
    
       
    
      *
    
      word)
    
      //
    
      查找，与插入类似
    
      

    
      {
 Treenode 
    
      *
    
      location
    
      =
    
      root;
 
    
      int
    
       i
    
      =
    
      0
    
      ,branch
    
      =
    
      0
    
      ,ans;

 
    
      if
    
      (location
    
      ==
    
      NULL) 
    
      return
    
       
    
      0
    
      ;

 
    
      while
    
      (word[i])
 {
 branch
    
      =
    
      word[i]
    
      -
    
      '
    
      a
    
      '
    
      ;
 
    
      if
    
      (
    
      !
    
      location
    
      ->
    
      next[branch]) 
    
      return
    
       
    
      0
    
      ;
 i
    
      ++
    
      ;
 location
    
      =
    
      location
    
      ->
    
      next[branch];
 ans
    
      =
    
      location
    
      ->
    
      count;
 }
 
    
      return
    
       ans;
}

    
      int
    
       main()
{
 
    
      char
    
       word[
    
      10
    
      ];
 
    
      char
    
       ask[
    
      10
    
      ];
 Treenode 
    
      *
    
      root
    
      =
    
      NULL;
 
    
      while
    
      (gets(word))
 {
 
    
      if
    
      (word[
    
      0
    
      ]
    
      ==
    
      '
    
      \0
    
      '
    
      ) 
    
      break
    
      ;
 insert(root,word);
 }
 
    
      while
    
      (gets(ask))
 cout
    
      <<
    
      search(root,ask)
    
      <<
    
      endl;
 
    
      return
    
       
    
      0
    
      ;
}