Implement Trie Prefix Tree

Driver Code

obj = Trie()
obj.insert(word)
param_2 = obj.search(word)
param_3 = obj.startsWith(prefix)

Solution

Trie

Note that when a key is not present, defaultdict(TreeNode)'s [key] would return a new TreeNode, whereas .get(key) would return nothing.

See more about Trie in Interview Algorithms.

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

class Trie:
    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.root = TrieNode()

    def insert(self, word: str) -> None:
        """
        Inserts a word into the trie.
        """
        curr = self.root
        for char in word:
            curr = curr.children[char]
        curr.is_word = True

    def search(self, word: str) -> bool:
        """
        Returns if the word is in the trie.
        """
        curr = self.root
        for char in word:
            curr = curr.children.get(char)
            if not curr:
                return False
        return curr.is_word

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