LeetCode 211. Add and Search Word - Data structure design

Posted on | In |
Words count in article: 265 | Reading time ≈ 1

题目

Design a data structure that supports the following two operations:

1
2
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:

1
2
3
4
5
6
7
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.

思路

Trie树.

代码

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
class Node(object):
    def __init__(self):
        self.children = collections.defaultdict(Node)
        self.isword = False
        
        
class WordDictionary(object):

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.root = Node()

    def addWord(self, word):
        """
        Adds a word into the data structure.
        :type word: str
        :rtype: None
        """
        current = self.root
        for w in word:
            current = current.children[w]
        current.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.match(word, 0, self.root)
    
    def match(self, word, index, root):
        if root == None:
            return False
        if index == len(word):
            return root.isword
        if word[index] != '.':
            return root != None and self.match(word, index + 1, root.children.get(word[index]))
        else:
            for child in root.children.values():
                if self.match(word, index + 1, child):
                    return True
        return False


# Your WordDictionary object will be instantiated and called as such:
# obj = WordDictionary()
# obj.addWord(word)
# param_2 = obj.search(word)