720. 词典中最长的单词

题目链接	720. 词典中最长的单词
思路	Trie树的经典应用
题解链接	官方题解
关键点	构建Trie树
时间复杂度	\(O(\sum_{i}\#\text{word}_{i})\)
空间复杂度	\(O(\sum_{i}\#\text{word}_{i})\)

代码实现：

class Trie:def __init__(self):self.children = [None] * 26self.isEnd = Falsedef insert(self, word):node = selffor ch in word:ch = ord(ch) - ord("a")if not node.children[ch]:node.children[ch] = Trie()node = node.children[ch]node.isEnd = Truedef search(self, word):node = selffor ch in word:ch = ord(ch) - ord("a")if node.children[ch] is None or not node.children[ch].isEnd:return Falsenode = node.children[ch]return Trueclass Solution:def longestWord(self, words: List[str]) -> str:tree = Trie()for word in words:tree.insert(word)answer = ""for word in words:if tree.search(word) and (len(word) > len(answer) or len(word) == len(answer) and word < answer):answer = wordreturn answer