LeetCode [1120] Maximum Average Subtree

1120. Maximum Average Subtree

Medium

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 an average of (5 + 6 + 1) / 3 = 4.
For the node with value = 6 we have an average of 6 / 1 = 6.
For the node with value = 1 we have an 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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/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val = val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val = val; * this.left = left; * this.right = right; * } * } */ class Solution { double maxAverage = Integer.MIN_VALUE; public double maximumAverageSubtree(TreeNode root) { helper(root); return maxAverage; } //sum, count double[] helper(TreeNode node){ if(node==null) return new double[0]; double sum = node.val, count = 1; if(node.left!=null){ double[] left = helper(node.left); sum += left[0]; count += left[1]; } if(node.right!=null){ double[] right = helper(node.right); sum += right[0]; count += right[1]; } maxAverage = Math.max(maxAverage, sum/count); return new double[]{sum, count}; } }