Find K-th Smallest Element in BST

Given a binary search tree (BST) and an integer K, the task is to find the K-th smallest element in the BST.

Example:

Input:

BST: Order of elements in increasing order is { 2, 3, 4, 5, 6, 7, 8, 10 }
K = 3

Output:

4

Explanation:

The 3rd smallest element in the BST is 4.

Constraints:

• 1 <= T <= 100
• 1 <= N, K <= 3000
• -10^9 <= data <= 10^9
• Time Limit: 1 sec

Note:

The input for the tree is provided in level order, using -1 for null nodes. The task is to find and return the K-th smallest element in the format described.