trie.py

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

Note:
You may assume that all inputs are consist of lowercase letters a-z.
"""
import collections


class TrieNode:
    def __init__(self):
        self.children = collections.defaultdict(TrieNode)
        self.is_word = False


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

    def insert(self, word):
        current = self.root
        for letter in word:
            current = current.children[letter]
        current.is_word = True

    def search(self, word):
        current = self.root
        for letter in word:
            current = current.children.get(letter)
            if current is None:
                return False
        return current.is_word

    def starts_with(self, prefix):
        current = self.root
        for letter in prefix:
            current = current.children.get(letter)
            if current is None:
                return False
        return True