Deepest Leaves Sum

Medium

Given the root of a binary tree, return the sum of values of its deepest leaves.

Example 1

Input:  root = [1,2,3,4,5,null,6,7,null,null,null,null,8]
Output: 15

Example 2

Input:  root = [6,7,8,2,7,1,3,9,null,1,4,null,null,null,5]
Output: 19

Constraints

• 1 <= number of nodes <= 10^4
• 1 <= Node.val <= 100