LeetCode：208. 实现 Trie (前缀树)

1、题目描述

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。

2、题解

2.1、解法一

class Trie(object):

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

    def insert(self, word):
        """
        Inserts a word into the trie.
        :type word: str
        :rtype: void
        """
        self.dic[word] = word
        i = 1
        while i < len(word)+1:
            self.prefix.add(word[:i])
            i += 1



    def search(self, word):
        """
        Returns if the word is in the trie.
        :type word: str
        :rtype: bool
        """
        return True if word in self.dic else False

    def startsWith(self, prefix):
        """
        Returns if there is any word in the trie that starts with the given prefix.
        :type prefix: str
        :rtype: bool
        """
        return True if prefix in self.prefix else False
        


# 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)