Deepest Leaves Sum

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

Examples

Example 1:

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

Output: 15

Explanation: The deepest leaves are nodes with values 7 and 8. Their sum is 7 + 8 = 15.

Example 2:

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

Output: 19

Explanation: The deepest leaves are nodes with values 9, 1, 4, and 5. Their sum is 9 + 1 + 4 + 5 = 19.

Example 3:

Input: root = [1]

Output: 1

Explanation: The only node is the deepest leaf.

Constraints

• The number of nodes in the tree is in the range [1, 10⁴]
• 1 <= Node.val <= 100