DAY168 - Complete String

https://www.codingninjas.com/codestudio/problems/complete-string_2687860?utm_source=youtube&utm_medium=affiliate&utm_campaign=striver_tries_videos&leftPanelTab=0
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from os import *
from sys import *
from collections import *
from math import *

from typing import *
class TrieNode:
    def __init__(self):
        self.children = [None]*26
        self.flag = False
class Trie:
    def __init__(self):
        self.root = TrieNode()
    def insert(self, word):
        newRoot = self.root
        for ch in word:
            alphabetIndex = ord(ch)-ord('a')
            if newRoot.children[alphabetIndex] == None:
                newRoot.children[alphabetIndex] = TrieNode()
            newRoot = newRoot.children[alphabetIndex]
        newRoot.flag = True
    def search(self, word):
        newRoot = self.root
        for ch in word:
            alphabetIndex = ord(ch) - ord('a')
            newRoot = newRoot.children[alphabetIndex]
            if newRoot.flag == False:
                return False
            
        return True
def completeString(n: int, a: List[str])-> str:
    trie = Trie()
    for word in a:
        trie.insert(word)
    maxString = ""
    maxSlen = 0
    for word in a:
        x = trie.search(word)
        # print(word,x)
        if not x:
            continue
        if len(word) == maxSlen:
            if word<maxString:
                maxString = word
        if len(word)>maxSlen:
            maxString = word
            maxSlen = len(word)
    if len(maxString) == 0:
        return None
    return maxString
    pass