[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 = 0;
            double summer = 0;
            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 = 0;
            int rightCounter = 0;
            double leftSummer = 0;
            double rightSummer = 0;

            double? leftSum = TreeTraverse(subTreeRoot.left,ref leftCounter,ref leftSummer);

            if (false == leftSum.HasValue)
            {
                leftSum = 0;
            }
            else
                counter++;

            double? rightSum = TreeTraverse(subTreeRoot.right,ref rightCounter,ref rightSummer);
            
            if (false == rightSum.HasValue)
            {
                rightSum = 0;
            }
            else
                counter++;

            counter = (leftCounter + rightCounter + 1);
            summer = (leftSummer + rightSummer + subTreeRoot.val);
            avgs.Add(summer / counter);

            return subTreeRoot.val;
        }
}