package top100liked

// https://leetcode.cn/problems/kth-smallest-element-in-a-bst/description/?envType=study-plan-v2&envId=top-100-liked

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

func kthSmallest(root *TreeNode, k int) int {
	res, cnt := 0, 0
	var helper func(node *TreeNode) bool
	helper = func(node *TreeNode) bool {
		if node == nil {
			return false
		}
		if helper(node.Left) {
			return true
		}
		cnt++
		if cnt == k {
			res = node.Val
			return true
		}
		return helper(node.Right)
	}
	helper(root)
	return res
}