211. Design Add and Search Words Data Structure

Medium

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

Implement the WordDictionary class:

• WordDictionary() Initializes the object.

• void addWord(word) Adds word to the data structure, it can be matched later.

• bool search(word) Returns true if there is any string in the data structure that matches word or false otherwise. word may contain dots '.' where dots can be matched with any letter.

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

Constraints:

• 1 <= word.length <= 500

• word in addWord consists lower-case English letters.

• word in search consist of '.' or lower-case English letters.

• At most 50000 calls will be made to addWord and search.

class WordDictionary:

    def __init__(self):
        self.root = {}

    def addWord(self, word: str) -> None:
        node =  self.root
        index = 0
        while index < len(word):
            if word[index] in node:
                node = node[word[index]]
                index += 1
                continue
            break
        while index < len(word):
            node[word[index]] = {}
            node = node[word[index]]
            index += 1
        node['$'] = {} # Word End Marking

    def search(self, word: str) -> bool:
        return self.recursive_search(word, self.root)
    
    def recursive_search(self, word:str, root):
        if not word and '$' in root:
            return True
        # print('Word', word)
        index = 0
        while index < len(word):
            char = word[index]
            if char == '.':
                result = []
                for key in root.keys():
                    if key != '$':
                        # print('Key', key)
                        result.append(self.recursive_search(word[index+1:], root[key]))
                return any(result)
            elif char not in root:
                return False
            elif char in root:
                root = root[char]
            index += 1
        return True if '$' in root else False


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