package q230

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func findKth(node *TreeNode, k, current int) (int, *int) {
	if node == nil {
		return current, nil
	}

	current, ret := findKth(node.Left, k, current)
	if ret != nil {
		return current, ret
	}

	current += 1
	if current == k {
		return current, &node.Val
	}

	return findKth(node.Right, k, current)
}

func kthSmallest(root *TreeNode, k int) int {
	_, kth := findKth(root, k, 0)
	if kth == nil {
		return 0
	}
	return *kth
}

var _ = kthSmallest