Trie Tree

Trie Tree

#Trie Tree的基本特点
1）根节点不包含字符，除根节点外每个节点只包含一个字符
2）从根节点到某一个节点，路径上经过的字符连接起来，为该节点对应的字符串
3）每个节点的所有子节点包含的字符串不相同

原理图：


参考：
数据结构之Trie树
Trie Tree on Answers.com

#Trie Tree简单的Python实现
最近在学习Python，下面的代码就用来学习下语法了 ：）

# coding:utf-8
'''
Created on 2011-6-14

@author: Dokie
'''
ALPHABET_SIZE  =   26

class  Node:
    
     def   __init__ (self, is_end  =  False):
        self.is_end  =  is_end
        self.prefix_count  =  0
        self.children  =  [None  for  child  in  range(ALPHABET_SIZE)]

class  Trie:
     def   __init__ (self):
        self.head  =  Node()
        
     def  insert(self, word):
        current  =  self.head
        count  =  0
         for  letter  in  word:
            int_value  =  ord(letter)  -  ord( ' a ' )
             try :
                 assert  ( 0  <=  int_value  <=   26 )
             except  Exception:
                 raise  Exception( " invalid Word " )
            
             if  current.children[int_value]  is  None:
                current.children[int_value]  =  Node()
                current  =  current.children[int_value]
                count  +=   1
                current.prefix_count  =  count
        current.is_end  =  True
        
     def  search(self, word):
        
        current  =  self.head
         for  letter  in  word:
            int_value  =  ord(letter)  -  ord( ' a ' )
             try :
                 assert  (0  <=  int_value  <=   26 )
             except  Exception:
                 return  False
             if  current.children[int_value]  is  None:
                 return  False
             else :
                current  =  current.children[int_value]
                
             return  current.is_end


        
        
         
     def  count_words_with_prefix(self, word):
        current  =  self.head
         for  letter  in  word:
            int_value  =  ord(letter)  -  ord( ' a ' )
             try :
                 assert  (0  <=  int_value  <=   26 )
             except  Exception:
                 return  None
             if  current.children[int_value]  is  None:
                 return  None
             else :
                current  =   current.children[int_value]
         return  current.prefix_count
                

        
if   __name__   ==   ' __main__ ' :
     import  doctest
    doctest.testmod()
    t  =  Trie()
    t.insert( " apple " )
    t.insert( " good " )
     print  t.search( " apple " )
     print  t.search( " fff " )
     print  t.count_words_with_prefix( " apple " )

附：TrieMap Javap实现