Deepest Leaves Sum

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

Example 1

        1
       / \
      2   3
     / \   \
    4   5   6
   /         \
  7           8

Inputroot = [1,2,3,4,5,null,6,7,null,null,null,null,8]

Output15

The deepest leaves have values 7 and 8, and their sum is 15.

Example 2

            6
          /   \
         7     8
        / \   / \
       2   7 1   3
      /   / \     \
     9   1   4     5

Inputroot = [6,7,8,2,7,1,3,9,null,1,4,null,null,null,5]

Output19

The deepest leaves have values 9, 1, 4, and 5, and their sum is 19.

Constraints