Average of Levels in Binary Tree

Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.

Example 1:

Input:
    3
   / 
  9  20
    /  
   15   7
Output: [3, 14.5, 11]
Explanation:
The average value of nodes on level 0 is 3,  on level 1 is 14.5, and on level 2 is 11. Hence return [3, 14.5, 11].

Note:

1. The range of node's value is in the range of 32-bit signed integer.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List<Double> averageOfLevels(TreeNode root) {
        List<Double> average = new ArrayList<>();
        if (root == null) return average;
        
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        while (queue.peek() != null) {
            average.add(0.0);
            int n = average.size() - 1;
            
            int levelCount = queue.size();
            int m = levelCount;
            while (levelCount-- != 0) {
                TreeNode temp = queue.poll();
                average.set(n, average.get(n) + temp.val);
                
                if (temp.left != null) queue.add(temp.left);
                if (temp.right != null) queue.add(temp.right);
            }
            average.set(n, average.get(n) / m);
        }
        return average;
    }
}

 

 

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List<Double> averageOfLevels(TreeNode root) {
        List<Double> sum = new ArrayList<Double>();
        List<Integer> count = new ArrayList<Integer>();
        
        levelTraversal(root, sum, count, 0);
        countAverage(sum, count);
        
        return sum;
    }
    
    private void levelTraversal(TreeNode root, List<Double> sum, List<Integer> count, int depth) {
        if (root == null) return;
        if (depth == sum.size()) {
            sum.add(0.0);
            count.add(0);
        }
        
        sum.set(depth, sum.get(depth) + root.val);
        count.set(depth, count.get(depth) + 1);
        
        levelTraversal(root.left, sum, count, depth + 1);
        levelTraversal(root.right, sum, count, depth + 1);
    }
    
    private void countAverage(List<Double> sum, List<Integer> count) {
        int n = sum.size();
        for (int i = 0; i < n; i++) {
            sum.set(i, sum.get(i) * 1.0 / count.get(i));
        }
    }
}