211. Add and Search Word - Data structure design

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.

解题要点：

用trie来存每个字符节点。以下大神解法！

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
        """
        node = self.root
        for char in word:
            node = node.setdefault(char, {})
        node[None] = None
        

    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 find(word, root):
            if not word:
                return None in root
            c, w = word[0], word[1:]
            if c != ".":
                return c in root and find(w, root[c])
            return any(find(w, k) for k in root.values() if k)
            
        return find(word, self.root)
        


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