Kth Smallest Element in BST

Given the root of a binary search tree, and an integer k, return the k^th smallest value (1-indexed) of all the values of the nodes in the tree.

Class TreeNode:
    val (int)
    left (TreeNode)
    right (TreeNode)

Input Format:

First Parameter - TreeNode root

Second Parameter - Number k

Output Format:

Return the number.

Example 1:

Input:
    3 1 4 null 2
    1    
Output:
    1

Example 2:

Input:
    5 3 6 2 4 null null 1
    3
Output:
    3

Constraints:

• The number of nodes in the tree is n
• 1 <= k <= n <= 10⁴
• 0 <= node.val <= 10⁴
• Expected Time Complexity: O(N)
• Expected SpaceComplexity: O(N)