[Leetcode] 1120. Maximum Average Subtree

Posted 2022-04-14 seako

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#

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 public class Solution 
 5     List<double> avgs = new List<double>();
 6     public double MaximumAverageSubtree(TreeNode root)
 7         
 8             int counter = 0;
 9             double summer = 0;
10             var result = TreeTraverse(root,ref counter,ref summer);
11 
12             return avgs.Max();
13         
14 
15         public double? TreeTraverse(TreeNode subTreeRoot,ref int counter,ref double summer)
16         
17             if(subTreeRoot == null)
18             
19                 return null;
20             
21             int leftCounter = 0;
22             int rightCounter = 0;
23             double leftSummer = 0;
24             double rightSummer = 0;
25 
26             double? leftSum = TreeTraverse(subTreeRoot.left,ref leftCounter,ref leftSummer);
27 
28             if (false == leftSum.HasValue)
29             
30                 leftSum = 0;
31             
32             else
33                 counter++;
34 
35             double? rightSum = TreeTraverse(subTreeRoot.right,ref rightCounter,ref rightSummer);
36             
37             if (false == rightSum.HasValue)
38             
39                 rightSum = 0;
40             
41             else
42                 counter++;
43 
44             counter = (leftCounter + rightCounter + 1);
45             summer = (leftSummer + rightSummer + subTreeRoot.val);
46             avgs.Add(summer / counter);
47 
48             return subTreeRoot.val;
49         
50