637. Average of Levels in Binary Tree 二叉树每一层的平均值

Posted 2020-09-27 Long Long Journey

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:

1. The range of node‘s value is in the range of 32-bit signed integer

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution(object):
    def averageOfLevels(self, root):
        """
        :type root: TreeNode
        :rtype: List[float]
        """        
        if(not root):
            return 0
        result = []
        queue = [root]
        while(queue):
            count = len(queue)
            sum = 0
            for i in range(0, count):
                node = queue.pop(0)
                sum += node.val
                if(node.left):
                    queue.append(node.left)
                if(node.right):
                    queue.append(node.right)
            result.append(sum * 1.0 / count)
        return result

来自为知笔记(Wiz)