leetcode [208] 实现 Trie (前缀树)

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Contact me:

Blog -> https://cugtyt.github.io/blog/index
Email -> cugtyt@qq.com
GitHub -> Cugtyt@GitHub

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实现一个 Trie (前缀树)，包含 insert, search, 和 startsWith 这三个操作。

示例:

Trie trie = new Trie();

trie.insert("apple");
trie.search("apple");   // 返回 true
trie.search("app");     // 返回 false
trie.startsWith("app"); // 返回 true
trie.insert("app");   
trie.search("app");     // 返回 true

说明:

你可以假设所有的输入都是由小写字母 a-z 构成的。 保证所有输入均为非空字符串。

class Trie:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.head = {}
        

    def insert(self, word: str) -> None:
        """
        Inserts a word into the trie.
        """
        head = self.head
        for w in word:
            if w not in head:
                head[w] = {}
            head = head[w]
        head[None] = None

    def search(self, word: str) -> bool:
        """
        Returns if the word is in the trie.
        """
        head = self.head
        for w in word:
            if w in head:
                head = head[w]
            else:
                return False
        if None in head:
            return True
        return False

    def startsWith(self, prefix: str) -> bool:
        """
        Returns if there is any word in the trie that starts with the given prefix.
        """
        head = self.head
        for w in prefix:
            if w in head:
                head = head[w]
            else:
                return False
        return True