637_Average of Levels in Binary Tree

102_Binary Tree Level Order Traversal 变形

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.

Solution

# 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]
        """
        res = []
        level = [root]
        while len(level) > 0:
            curLevel = [node.val for node in level]
            res.append(float(sum(curLevel))/len(curLevel))
            temp = []
            for node in level:
                if node.left != None:
                    temp.append(node.left)
                if node.right != None:
                    temp.append(node.right)
            level = temp
        return res