211. Design Add and Search Words Data Structure

Problem Link

Description

---

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 <= 25
• word in addWord consists of lowercase English letters.
• word in search consist of '.' or lowercase English letters.
• There will be at most 2 dots in word for search queries.
• At most 104 calls will be made to addWord and search.

Solution

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Python3

class TrieNode:
    def __init__(self):
        self.children = {}
        self.hasWord = False
 
class WordDictionary:
 
    def __init__(self):
        self.root = TrieNode()
 
    def addWord(self, word: str) -> None:
        curr = self.root
 
        for x in word:
            if x not in curr.children:
                curr.children[x] = TrieNode()
            
            curr = curr.children[x]
        
        curr.hasWord = True
 
    def search(self, word: str) -> bool:
        N = len(word)
 
        def go(index, curr):
            if index == N: return curr.hasWord
            
            x = word[index]
 
            if x == '.':
                for child in curr.children:
                    if go(index + 1, curr.children[child]):
                        return True
            else:
                if x in curr.children:
                    if go(index + 1, curr.children[x]):
                        return True
                else:
                    return False
            
            return False
 
        return go(0, self.root)
        
 
 
# Your WordDictionary object will be instantiated and called as such:
# obj = WordDictionary()
# obj.addWord(word)
# param_2 = obj.search(word)