Leetcode 211.添加與搜索單詞 - 數據結構設計
1 題目描述(Leetcode題目鏈接)
設計一個支持以下兩種操作的數據結構:
void addWord(word)
bool search(word)
search(word) 可以搜索文字或正則表達式字符串,字符串只包含字母 . 或 a-z 。 . 可以表示任何一個字母。
addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true
說明:你可以假設所有單詞都是由小寫字母 a-z 組成的
2 題解
本題爲字典樹的基本操作的實現,可以參照第208題,這裏由於存在通配符,所以如果遇到通配符就需要遍歷當前層的所有子節點,用深度優先搜索遞歸實現就可以了。
class TreeNode:
def __init__(self):
self.children = collections.defaultdict(TreeNode)
self.end = False
class WordDictionary:
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = TreeNode()
def addWord(self, word: str) -> None:
"""
Adds a word into the data structure.
"""
node = self.root
for char in word:
node = node.children[char]
node.end = True
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.
"""
length = len(word)
def dfs(node, i):
if i == length:
return node.end
if word[i] != ".":
node = node.children.get(word[i])
if node:
return dfs(node, i + 1)
return False
else:
for char in node.children:
if dfs(node.children[char], i + 1):
return True
return False
return dfs(self.root, 0)
# Your WordDictionary object will be instantiated and called as such:
# obj = WordDictionary()
# obj.addWord(word)
# param_2 = obj.search(word)