字典树的实现（Python）

接着上一篇字典树结构的讲解，我们接着使用C++和Python来实现字典树。

一、LeetCode的字典树

在LeetCode 208 要求实现字典树。

Implement a trie with insert, search, and startsWith methods.
Note:
You may assume that all inputs are consist of lowercase letters a-z.

二、Python实现

# coding:utf-8
""" Implement a trie with insert, search, and startsWith methods. Note: You may assume that all inputs are consist of lowercase letters a-z. Subscribe to see which companies asked this question """


class TrieNode(object):
    def __init__(self):
        """ Initialize your data structure here. """
        self.data = {}
        self.is_word = False


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.data.get(letter)
            if not child:
                node.data[letter] = TrieNode()
            node = node.data[letter]
        node.is_word = 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:
            node = node.data.get(letter)
            if not node:
                return False
        return node.is_word  # 判断单词是否是完整的存在在trie树中

    def starts_with(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:
            node = node.data.get(letter)
            if not node:
                return False
        return True

    def get_start(self, prefix):
        """ Returns words started with prefix :param prefix: :return: words (list) """
        def _get_key(pre, pre_node):
            words_list = []
            if pre_node.is_word:
                words_list.append(pre)
            for x in pre_node.data.keys():
                words_list.extend(_get_key(pre + str(x), pre_node.data.get(x)))
            return words_list

        words = []
        if not self.starts_with(prefix):
            return words
        if self.search(prefix):
            words.append(prefix)
            return words
        node = self.root
        for letter in prefix:
            node = node.data.get(letter)
        return _get_key(prefix, node)


# Your Trie object will be instantiated and called as such:
trie = Trie()
trie.insert("somestring")
trie.insert("somebody")
trie.insert("somebody1")
trie.insert("somebody3")
print trie.search("key")
print trie.search("somebody3")
print trie.get_start('some')

结构

输出

# print trie.search("key")
False
# print trie.search("somebody3")
True
# print trie.get_start('some')
['somestring', 'somebody', 'somebody1', 'somebody3']

采用Class来实现字典树：https://github.com/bdimmick/python-trie/blob/master/trie.py

三、C++实现

TODO

四、字典树的应用

1. 搜索框的自动完成功能





2. T9输入的自动联想