leetcode 208. 实现 Trie (前缀树)

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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。
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class TrieNode:
    def __init__(self):
        self.child = {}
        self.end = False
        
class Trie:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.root = TrieNode()
        

    def insert(self, word):
        """
        Inserts a word into the trie.
        :type word: str
        :rtype: void
        """
        current = self.root
        for ch in word:
            node = current.child.get(ch)
            if not node:
                node = TrieNode()
                current.child[ch] = node
            current = node
        current.end = True

    def search(self, word):
        """
        Returns if the word is in the trie.
        :type word: str
        :rtype: bool
        """
        curr = self.root
        for ch in word:
            if ch not in curr.child.keys():
                return False
            curr = curr.child[ch]
        return curr.end

    def startsWith(self, prefix):
        """
        Returns if there is any word in the trie that starts with the given prefix.
        :type prefix: str
        :rtype: bool
        """
        curr = self.root
        for ch in prefix:
            if ch not in curr.child.keys():
                return False
            curr = curr.child[ch]
        return True


# Your Trie object will be instantiated and called as such:
# obj = Trie()
# obj.insert(word)
# param_2 = obj.search(word)
# param_3 = obj.startsWith(prefix)