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Design Add and Search Words Data Structure

Problem Statement​

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.

LeetCode link

Example 1:​

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 <= 25
  • word in addWord consists of lowercase English letters.
  • word in search consist of '.' or lowercase English letters.
  • There will be at most 3 dots in word for search queries.
  • At most 104 calls will be made to addWord and search.

Code​

Python Code
class WordDictionary(object):
    def __init__(self):
        self.word_dict = collections.defaultdict(list)


    def addWord(self, word):
        if word:
            self.word_dict[len(word)].append(word)

    def search(self, word):
        if not word:
            return False
        if '.' not in word:
            return word in self.word_dict[len(word)]
        for v in self.word_dict[len(word)]:
            # match xx.xx.x with yyyyyyy
            for i, ch in enumerate(word):
                if ch != v[i] and ch != '.':
                    break
            else:
                return True
        return False