Leetcode 637 - Average levels in binary tree

Note:

  • Use level order traversal.

Given the root of a binary tree, return the average value of the nodes on each level in the form of an array. Answers within 10-5 of the actual answer will be accepted.

Example

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Input: root = [3,9,20,null,null,15,7]
Output: [3.00000,14.50000,11.00000]
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].
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/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {TreeNode} root
* @return {number[]}
*/
var averageOfLevels = function(root) {
let result = [];
if (!root) return 0;
let queue = [root];
while (queue.length) {
let length = queue.length;
let sum = 0;
for (let i = 0; i < length; i++) {
let node = queue.shift();
sum += node.val;
node.left && queue.push(node.left);
node.right && queue.push(node.right);
}
result.push(sum / length);
}
return result;
};