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implement-trie-prefix-tree.py
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implement-trie-prefix-tree.py
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# Time: O(n), per operation
# Space: O(1)
#
# Implement a trie with insert, search, and startsWith methods.
#
# Note:
# You may assume that all inputs are consist of lowercase letters a-z.
#
class TrieNode:
# Initialize your data structure here.
def __init__(self):
self.is_string = False
self.leaves = {}
class Trie:
def __init__(self):
self.root = TrieNode()
# @param {string} word
# @return {void}
# Inserts a word into the trie.
def insert(self, word):
cur = self.root
for c in word:
if not c in cur.leaves:
cur.leaves[c] = TrieNode()
cur = cur.leaves[c]
cur.is_string = True
# @param {string} word
# @return {boolean}
# Returns if the word is in the trie.
def search(self, word):
node = self.childSearch(word)
if node:
return node.is_string
return False
# @param {string} prefix
# @return {boolean}
# Returns if there is any word in the trie
# that starts with the given prefix.
def startsWith(self, prefix):
return self.childSearch(prefix) is not None
def childSearch(self, word):
cur = self.root
for c in word:
if c in cur.leaves:
cur = cur.leaves[c]
else:
return None
return cur
# Your Trie object will be instantiated and called as such:
# trie = Trie()
# trie.insert("somestring")
# trie.search("key")