1302. Deepest Leaves Sum

https://leetcode.com/problems/deepest-leaves-sum/

Python

Sum Levels with preorder travel

class Solution:
    def deepestLeavesSum(self, root: Optional[TreeNode]) -> int:
        level_counts = []

        def preorder(node, level):
            if not node:
                return

            if level == len(level_counts):
                level_counts.append(0)

            level_counts[level] += node.val
            preorder(node.left, level+1)
            preorder(node.right, level+1)

        preorder(root, 0)

        return level_counts[-1]

Javascript

var deepestLeavesSum = function(root) {
    const queue = [root];
    let level = 0;
    const layer = [];

    while (queue.length) {
      const total = queue.length;
      layer.push([]);
      for (let i = 0; i < total; i++) {
        const node = queue.shift();
        layer[level].push(node.val);

        if (node.left) queue.push(node.left);
        if (node.right) queue.push(node.right);
      }
      level++;
    }

    return layer[layer.length - 1].reduce((acc, cur) => acc + cur, 0)
}