# [LeetCode]#637. Average of Levels in Binary Tree

Environment: Python 3.8

Key technique: binarytree, Node, collections, deque

Given the `root` of a binary tree, return the average value of the nodes on each level in the form of an array. Answers within `10-5` of the actual answer will be accepted.

Example 1:

`Input: root = [3,9,20,null,15,7]Output: [3.00000,14.50000,11.00000]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].`

Analysis:

1. Use collections.deque()

Solution:

`from binarytree import Noderoot = Node(3) root.left=Node(9)root.right=Node(20) root.right.left=Node(15)root.right.right=Node(7)# Getting binary tree print('Binary tree :', root)import collectionsclass Solution(object):    def averageOfLevels(self, root):        queue = collections.deque()        ans = []        queue.append(root)        while queue:            size = len(queue)            temp = []            for _ in range(size):                node = queue.popleft()                if not node:                    continue                temp.append(node.val)                queue.append(node.left)                queue.append(node.right)            if temp:                ans.append(sum(temp) / float(len(temp)))        return ans`

Submissions:

Reference:

Note: Not so good for node.

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