Leetcode-211. Add and Search Word - Data structure design

一、题目描述

 

Design a data structure that supports the following two operations:

void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.

Example:

addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

Note:
You may assume that all words are consist of lowercase letters a-z.

 

二、解法，这个题目我用普通方法实现，结果超时了

　　

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class Word:     def __init__(self, s):         self.s = s       def __eq__(self, other):         if isinstance(other, Word):             if not self.s or not other.s:                 return self.s == other.s             if len(self.s) != len(other.s):                 return False             for i in range(len(self.s)):                 if self.s[i] != other.s[i] and self.s[i] != '.' and other.s[i] != '.':                     return False             return True                   def __str__(self):         return self.s               def __hash__(self):         return hash(str(self))   class WordDictionary:       def __init__(self):         """         Initialize your data structure here.         """         self.m = {}                 def addWord(self, word):         """         Adds a word into the data structure.         :type word: str         :rtype: void         """         key = Word(word)         if key in self.m:             self.m[key] += 1         else:             self.m[key] = 1       def search(self, word):         """         Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter.         :type word: str         :rtype: bool         """         key = Word(word)         if key in self.m:             return True                   for k in self.m:             if k == key:                 return True                           return False

　　这个题目的本质是字典树，使用字典树才不会超时

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class WordDictionary:           class TrieNode:         def __init__(self):             self.isword = False             self.child = [None for i in range(26)]       def __init__(self):         """         Initialize your data structure here.         """         self.root = WordDictionary.TrieNode()                 def addWord(self, word):         """         Adds a word into the data structure.         :type word: str         :rtype: void         """         p = self.root         for c in word:             i = ord(c) - ord('a')             if not p.child[i]:                 p.child[i] = WordDictionary.TrieNode()             p = p.child[i]         p.isword = True       def search(self, word):         """         Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter.         :type word: str         :rtype: bool         """         return self.searchNode(word, self.root, 0)               def searchNode(self, word, node, i):         if i == len(word):             return node.isword         if word[i] == '.':             for a in node.child:                 if a and self.searchNode(word, a, i+1):                     return True             return False         else:             index = ord(word[i]) - ord('a')             return node.child[index] != None and self.searchNode(word, node.child[index], i+1)

　　注意python和C语言的不同

　

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def hello():     x = None     return (x and False) == None       def hello2():     x = None     return (x and False)

　　输出

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True   None