public class Solution
extends Object
230 - Kth Smallest Element in a BST\.
Medium
Given the `root` of a binary search tree, and an integer `k`, return _the_ kth _smallest value ( **1-indexed** ) of all the values of the nodes in the tree_.
**Example 1:**
**Input:** root = [3,1,4,null,2], k = 1
**Output:** 1
**Example 2:**
**Input:** root = [5,3,6,2,4,null,null,1], k = 3
**Output:** 3
**Constraints:**
* The number of nodes in the tree is `n`.
* 1 <= k <= n <= 104
* 0 <= Node.val <= 104
**Follow up:** If the BST is modified often (i.e., we can do insert and delete operations) and you need to find the kth smallest frequently, how would you optimize?