Implement_Trie_(Prefix_Tree).md

208. Implement Trie (Prefix Tree)

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

Note:

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

Method:

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

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
        """
        cur=self.root
        for letter in word:
            cur=cur.children[letter]
        cur.is_word=True
            
    def search(self, word):
        """
        Returns if the word is in the trie.
        :type word: str
        :rtype: bool
        """
        cur=self.root
        for letter in word:
            if cur.children.get(letter)==None:
                return False
            cur=cur.children[letter]
        return cur.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
        """
        cur=self.root
        for letter in prefix:
            if cur.children.get(letter)==None:
                return False
            cur=cur.children[letter]
        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)

Solution:

class Trie(object):

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

    def insert(self, word):
        """
        Inserts a word into the trie.
        :type word: str
        :rtype: void
        """
        cur=self.root
        for letter in word:
            if letter not in cur:
                cur[letter]={}
            cur=cur[letter]
        cur["is_word"]=True
            
    def search(self, word):
        """
        Returns if the word is in the trie.
        :type word: str
        :rtype: bool
        """
        cur=self.root
        for letter in word:
            if letter not in cur:
                return False
            cur=cur[letter]
        return "is_word" in cur
        

    def startsWith(self, prefix):
        """
        Returns if there is any word in the trie that starts with the given prefix.
        :type prefix: str
        :rtype: bool
        """
        cur=self.root
        for letter in prefix:
            if letter not in cur:
                return False
            cur=cur[letter]
        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)