# Definition for a binary tree node.# class TreeNode:#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Nonefrom collections import dequeclass Solution:    def averageOfLevels(self, root):        """        :type root: TreeNode        :rtype: List[float]        """        res = []        q = deque([root])        while q:            curr_sum = 0            node_num_this_layer = len(q)            for i in range(0, node_num_this_layer):                node = q.popleft();                curr_sum += node.val                if node.left:                    q.append(node.left)                if node.right:                    q.append(node.right)            res.append(1.0*curr_sum/node_num_this_layer)        return res