README.md

211. Design Add and Search Words Data Structure

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.

Solutions (Python)

1. Solution

class WordDictionary:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.children = [None] * 26
        self.is_end = False

    def addWord(self, word: str) -> None:
        """
        Adds a word into the data structure.
        """
        i = ord(word[0]) - 97

        if not self.children[i]:
            self.children[i] = WordDictionary()

        if len(word) == 1:
            self.children[i].is_end = True
        else:
            self.children[i].addWord(word[1:])

    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.
        """
        i = ord(word[0]) - 97

        if word == '.':
            return any(child.is_end for child in self.children if child)
        elif len(word) == 1:
            return self.children[i] and self.children[i].is_end
        elif word[0] == '.':
            return any(child.search(word[1:]) for child in self.children if child)
        else:
            return self.children[i] and self.children[i].search(word[1:])


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