# Leetcode: Implement Trie (Prefix Tree)

Implement Trie (Prefix Tree)

Similar Problems:

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

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

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

```## Blog link: https://code.dennyzhang.com/implement-trie-prefix-tree
## Basic Ideas: TrieNode: is_word(bool), children(dict)
##           For the root node, we don't store any characters. Only in children
##           Here we use defaultdict, thus we can avoid has_key check
## Assumption: If one word in the Trie tree, we also treat it starts with the word.
## Complexity:

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

class Trie(object):

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

def insert(self, word):
"""
Inserts a word into the trie.
:type word: str
:rtype: void
"""
node = self.root
# check character by character
for ch in word:
node = node.children[ch]
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 ch in word:
if ch not in node.children:
return False
node = node.children[ch]
return node.is_word

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 ch in prefix:
if ch not in node.children:
return False
node = node.children[ch]
return True

# 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)
```

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