[Leetcode] Binary tree-- 637. Average of Levels in Binary Tree

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   7Output: [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, 1


Solution:

   # it actually examines the knowledge of level order
   #refer to the similar problem : 102. Binary Tree Level Order Traversal

 1         if not root: 2             return [] 3         d = collections.deque() 4         d.append(root) 5         resLst = [] 6         while(len(d)): 7             n = len(d) 8             lst = [] 9             tmpSum = 0.010             count = n11             while(n > 0):12                 node = d.popleft()13                 tmpSum += node.val14                 if node.left:15                     d.append(node.left)16                 if node.right:17                     d.append(node.right)18                 n -= 119             resLst.append(tmpSum/count)20 21         return resLst