設計一個支持以下兩種操作的數據結構：
void addWord(word) bool search(word)
search(word) 可以搜索文字或正則表達式字符串，字符串只包含字母 . 或 a-z 。 . 可以表示任何一個字母。
示例:
addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true
說明:
你可以假設所有單詞都是由小寫字母 a-z 組成的。
這道理兩種做法，字典樹或者前綴樹。但是由於題目是考察前綴樹的，所以字典樹的時間效率很差。
字典樹
class WordDictionary(object):
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = {}
def addWord(self, word):
"""
Adds a word into the data structure.
:type word: str
:rtype: None
"""
tmp = self.root
for i in word:
if i not in tmp:
tmp[i] = {}
tmp = tmp[i]
tmp['end'] = 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
"""
def check(word, tmp):
if word == '':
if 'end' in tmp:
return True
return False
elif 'end' in tmp and len(tmp)==1:
return False
if word[0] in tmp and check(word[1:], tmp[word[0]]):
return True
if word[0] == '.':
for i in tmp:
if i != 'end' and check(word[1:], tmp[i]):
return True
return False
return check(word, self.root)
前綴樹
class WordDictionary(object):
def __init__(self):
"""
Initialize your data structure here.
"""
from collections import defaultdict
self.word_dict = defaultdict(list)
def addWord(self, word):
"""
Adds a word into the data structure.
:type word: str
:rtype: void
"""
self.word_dict[len(word)].append(word)
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
"""
for item in self.word_dict[len(word)]:
flag = False
for x,y in zip(item,word):
if y == "." or x == y:
continue
else:
flag = True
break
if not flag :
return True
return False