Implement Trie - 卖萌的弱渣

Implement a trie with insert, search, and startsWith methods.

Note:

You may assume that all inputs are consist of lowercase letters a-z.

Solution

本题考查字典树数据结构的基础知识。
Trie使用孩子表示法存储，TrieNode为字典树的节点，包含属性childs和isWord。
其中childs为dict，存储当前节点的后代节点；isWord为布尔值，表示当前节点是否存储了一个单词。

(Implement-Trie.py) download

class TrieNode(object):
    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.isWord = False
        # if this node has a word
        self.children = dict()
        # all children nodes

class Trie(object):

    def __init__(self):
        self.root = TrieNode()

    def insert(self, word):
        """
        Inserts a word into the trie.
        :type word: str
        :rtype: void
        """
        node = self.root
        for letter in word:
            child = node.children.get(letter)
            if child == None:
                child = TrieNode()
                node.children[letter] = child
            node = child
        node.isWord = True

    def search(self, word):
        """
        Returns if the word is in the trie.
        :type word: str
        :rtype: bool
        """
        node = self.root
        for letter in word:
            child = node.children.get(letter)
            if child == None:
                return False
            node = child
        if node.isWord == True:
            return True
        else:
            return 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
        """
        node = self.root

        for letter in prefix:
            child = node.children.get(letter)
            if child == None:
                return False
            node = child
        return True

# Your Trie object will be instantiated and called as such:
# trie = Trie()
# trie.insert("somestring")
# trie.search("key")