python数据结构与算法——字典树

 1 class TrieTree():
 2     def __init__(self):
 3         self.root = {}
 4     
 5     def addNode(self,str):
 6         # 树中每个结点(除根节点)，包含到该结点的单词数，以及该结点后面出现字母的键
 7         nowdict = self.root
 8         for i in range(len(str)):
 9             if str[i] not in nowdict:    # 发现新的组合方式
10                 nowdict[str[i]] = {‘count‘:0,‘prefix‘:str[:i+1]}
11             nowdict = nowdict[str[i]]    # 转移到下一个结点
12         nowdict[‘count‘] += 1
13     
14     def countWord(self,str):
15         # 返回输入单词在树中出现的次数
16         nowdict = self.root
17         for s in str:
18             if s not in nowdict:
19                 return 0
20             nowdict = nowdict[s]    # 匹配当前结点,转下一个结点
21         # 到了这一步证明单词存在
22         return nowdict[‘count‘]
23 
24 
25 
26 
27 
28 if __name__=="__main__":
29     pass
30     Text = [‘b‘,‘abc‘,‘abd‘,‘bcd‘,‘abcd‘,‘efg‘,‘hii‘,‘bcd‘]
31     t = TrieTree()
32     for str in Text:
33         t.addNode(str)
34     print t.countWord(‘bcd‘)
35 
36 >>> 2