[Leet Code] Maximum Level Sum of a Binary Tree

Leetcode: https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree/

Problem:

Given the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on.

Return the smallest level X such that the sum of all the values of nodes at level X is maximal.

Example 1:

Input: root = [1,7,0,7,-8,null,null]
Output: 2
Explanation: 
Level 1 sum = 1.
Level 2 sum = 7 + 0 = 7.
Level 3 sum = 7 + -8 = -1.
So we return the level with the maximum sum which is level 2.

Example 2:

Input: root = [989,null,10250,98693,-89388,null,null,null,-32127]
Output: 2

Solution:

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def maxLevelSum(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if root:
            elements = [[root.val]]
            stack = [root]
            self.helper(elements, stack)
            answers = []
            for i in elements:
                total = 0
                for j in i:
                    total += int(j)
                answers.append(total)
            return answers.index(max(answers)) + 1
        
    def helper(self, elements, stack):
        while len(stack) > 0:
            values = []
            length = len(stack)
            for i in range(length):
                node = stack.pop(0)
                if node.left:
                    stack.append(node.left)
                    values.append(node.left.val)
                if node.right:
                    stack.append(node.right)
                    values.append(node.right.val)
            if values != []:
                elements.append(values)