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211. Design Add and Search Words Data Structure

You should design a data structure that supports adding new words and finding if a string matches any previously added string.

Implement the WordDictionary class:

Example:

Input
["WordDictionary","addWord","addWord","addWord","search","search","search","search"]
[[],["bad"],["dad"],["mad"],["pad"],["bad"],[".ad"],["b.."]]
Output
[null,null,null,null,false,true,true,true]

Explanation
WordDictionary wordDictionary = new WordDictionary();
wordDictionary.addWord("bad");
wordDictionary.addWord("dad");
wordDictionary.addWord("mad");
wordDictionary.search("pad"); // return False
wordDictionary.search("bad"); // return True
wordDictionary.search(".ad"); // return True
wordDictionary.search("b.."); // return True

Solution

class trie_node:
    def __init__(self):
        self.valid = False
        self.children = dict()

class WordDictionary:

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

    def addWord(self, word: str) -> None:
        """
        Adds a word into the data structure.
        """
        node = self.root
        for l in word:
            if l not in node.children:
                node.children[l] = trie_node()
            node = node.children[l]
        node.valid = True
        

    def search(self, word: str) -> bool:
        """
        Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter.
        """
        return self.dc(word, self.root)
        
    def dc(self, word, node):
        if len(word) == 0:
            return node.valid
        
        if word[0] != '.':
            if word[0] not in node.children:
                return False
            return self.dc(word[1:], node.children[word[0]])
            
        # return true is there is a true, use "or"
        ans = False
        for k in node.children.keys():
            ans = ans or self.dc(word[1:], node.children[k])
        return ans