Implement Trie Prefix Tree

class Node:
    def __init__(self, letter = None):
        self.letter = letter
        self.child = {}
        self.isFinalLetter = False
 
class Trie:    
    def __init__(self):
        self.rootNode = Node()
 
    def insert(self, word: str) -> None:
        node = self.rootNode
        for c in word:
            if c not in node.child.keys():
                node.child[c] = Node(c)
            
            node = node.child[c]
        
        node.isFinalLetter = True
            
            
    def search(self, word: str) -> bool:
        node = self.rootNode
        for c in word:
            if c not in node.child.keys():
                print(node.child.keys())
                print(word)
                return False
            node = node.child[c]
 
        return node.isFinalLetter
        
 
    def startsWith(self, prefix: str) -> bool:
        node = self.rootNode
        n = len(prefix)
        if n == 0:
            return True
 
        counter = 0
        for c in prefix:
            if c not in node.child.keys():
                return False
 
            node = node.child[c]
            counter += 1
            if counter == n:
                return True
                
        return False
 
# 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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References

https://leetcode.com/problems/implement-trie-prefix-tree/