[Leetcode] 1120. Maximum Average Subtree

Given the root of a binary tree, find the maximum average value of any subtree of that tree.

(A subtree of a tree is any node of that tree plus all its descendants. The average value of a tree is the sum of its values, divided by the number of nodes.)

Example 1:

Input: [5,6,1]
Output: 6.00000
Explanation:
For the node with value = 5 we have and average of (5 + 6 + 1) / 3 = 4.
For the node with value = 6 we have and average of 6 / 1 = 6.
For the node with value = 1 we have and average of 1 / 1 = 1.
So the answer is 6 which is the maximum.

Note:

1. The number of nodes in the tree is between 1 and 5000.
2. Each node will have a value between 0 and 100000.
3. Answers will be accepted as correct if they are within 10^-5 of the correct answer.

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C#

 using System;
 using System.Collections.Generic;
 using System.Linq;
 public class Solution {
     List<double> avgs = new List<double>();
     public double MaximumAverageSubtree(TreeNode root)
         {
             int counter = ;
             double summer = ;
             var result = TreeTraverse(root,ref counter,ref summer);
 
             return avgs.Max();
         }
 
         public double? TreeTraverse(TreeNode subTreeRoot,ref int counter,ref double summer)
         {
             if(subTreeRoot == null)
             {
                 return null;
             }
             int leftCounter = ;
             int rightCounter = ;
             double leftSummer = ;
             double rightSummer = ;
 
             double? leftSum = TreeTraverse(subTreeRoot.left,ref leftCounter,ref leftSummer);
 
             if (false == leftSum.HasValue)
             {
                 leftSum = ;
             }
             else
                 counter++;
 
             double? rightSum = TreeTraverse(subTreeRoot.right,ref rightCounter,ref rightSummer);
 
             if (false == rightSum.HasValue)
             {
                 rightSum = ;
             }
             else
                 counter++;
 
             counter = (leftCounter + rightCounter + );
             summer = (leftSummer + rightSummer + subTreeRoot.val);
             avgs.Add(summer / counter);
 
             return subTreeRoot.val;
         }
 }