leetcode1120

 1 class Solution:
 2     def __init__(self):
 3         self.maxAvg = 0
 4 
 5     def preOrder(self,node):
 6         if node == None:
 7             return 0,0
 8         if node.left == None and node.right == None:
 9             self.maxAvg = max(self.maxAvg,node.val)
10             return 1,node.val
11         leftcount,leftsum,rightcount,rightsum = 0,0,0,0
12         if node.left != None:
13             leftcount,leftsum = self.preOrder(node.left)
14         if node.right != None:
15             rightcount,rightsum = self.preOrder(node.right)
16         totalcount = leftcount + rightcount + 1
17         totalsum = leftsum + rightsum + node.val
18         avg = totalsum / totalcount
19         self.maxAvg = max(self.maxAvg,avg)
20         return totalcount,totalsum
21 
22     def maximumAverageSubtree(self, root: TreeNode) -> float:
23         self.preOrder(root)
24         return self.maxAvg