LeetCode: Average of Levels in Binary Tree

LeetCode: 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:

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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.
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/**
* 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> result = new ArrayList<>();
if (root == null) {
return result;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
queue.add(null);
long sum = 0;
int count = 0;
while (!queue.isEmpty()) {
TreeNode node = queue.poll();
if (node == null) {
if (count != 0) {
result.add(1.0 * sum / count);
queue.add(null);
}
sum = count = 0;
continue;
}
count++;
sum += node.val;
if (node.left != null) {
queue.add(node.left);
}
if (node.right != null) {
queue.add(node.right);
}
}
return result;
}
}