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

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

# 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

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