211. Design Add and Search Words Data Structure

Medium (Trung bình) Python 🔗 Xem trên LeetCode

📋 Đề Bài

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 3 dots in word for search queries.
  • At most 104 calls will be made to addWord and search.

🧠 Thuật Toán & Kỹ Thuật

DFS (Tìm kiếm theo chiều sâu)Hash Table (Bảng băm)Trie (Cây tiền tố)
⏱️ Thời gian O(V+E)
💾 Không gian O(V)

💻 Lời Giải

Python 0211-design-add-and-search-words-data-structure.py 
class TrieNode:
    def __init__(self):
        self.isEndWord = False
        self.children = defaultdict(TrieNode)       

class WordDictionary:

    def __init__(self):
        self.root = TrieNode()

    def addWord(self, word: str) -> None:
        root = self.root
        
        for char in word:
            root = root.children[char]
            
        root.isEndWord = True

    def search(self, word: str) -> bool:
        def dfs(word, root):
            if not word:
                return root.isEndWord
            
            if word[0] != '.':
                if word[0] not in root.children:
                    return False
                if dfs(word[1:], root.children[word[0]]):
                    return True
            else:
                for node in root.children.values():
                    if dfs(word[1:], node):
                        return True
                    
            return False
        
        return dfs(word, self.root)
            


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