# Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.
#
# Example 1:
#
# Input:
#     3
#    / \
#   9  20
#     /  \
#    15   7
# Output: [3, 14.5, 11]
# Explanation:
# The average value of nodes on level 0 is 3,  on level 1 is 14.5, and on level 2 is 11. Hence return [3, 14.5, 11].
#
#
#
# Note:
#
# The range of node's value is in the range of 32-bit signed integer.
#
#


# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def averageOfLevels(self, root: TreeNode) -> List[float]:
        Avgs = []
        if root is None:
            return Avgs
        else:
            Avgs.append(root.val)
            fathers = []
            fathers.append(root)

            while fathers:
                childrens = []
                sum_of_childs, no_of_childs = 0, 0

                for f in fathers:
                    if f.right:
                        childrens += [f.right]

                    if f.left:
                        childrens += [f.left]

                for c in childrens:
                    if c:
                        sum_of_childs += c.val
                        no_of_childs += 1

                fathers = childrens

                if no_of_childs:
                    Avgs += [sum_of_childs / no_of_childs]

        return Avgs
