Solution1302.kt

class Solution {

    val leaves = mutableListOf<Pair<TreeNode, Int>>()
    var depth = 1
    fun deepestLeavesSum(root: TreeNode?): Int {
        if (root == null) return 0
        calcdepth(root)
        val maxdepth = leaves.map { it.second }.maxBy { it }
        return leaves.filter { it.second == maxdepth }.sumBy { it.first.`val` }
    }

    private fun calcdepth(root: TreeNode) {
        if (root.left == null && root.right == null) {
            leaves.add(Pair(root, depth--))
            return
        }
        if (root.left != null) {
            depth++
            calcdepth(root.left!!)
        }
        if (root.right != null) {
            depth++
            calcdepth(root.right!!)
        }
        if (root.left == null || root.right == null) depth--
        if (root.left != null && root.right != null) depth--
    }
}