前缀树

208. 实现 Trie (前缀树)

难度 ⭐⭐

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

Trie有什么用？

1. 自动补全

2. 拼写检查

coding

python

class Trie:

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

    def insert(self, word: str) -> None:
        """
        Inserts a word into the trie.
        """
        cur_node = self.root
        for c in word:
            cur_node = cur_node.setdefault(c,{})
        cur_node[self.is_end] = True

    def search(self, word: str) -> bool:
        """
        Returns if the word is in the trie.
        """
        cur_node = self.root
        for c in word:
            if c not in cur_node:
                return False
            cur_node = cur_node[c]
        
        return True if self.is_end in cur_node else False

    def startsWith(self, prefix: str) -> bool:
        """
        Returns if there is any word in the trie that starts with the given prefix.
        """
        cur_node = self.root
        for c in prefix:
            if c not in cur_node:
                return False
            cur_node = cur_node[c]
        return True