Problem: Kth Smallest Element in a BST

Given the root node of a binary search tree and an integer value k, return the $k^{th}$ smallest value in the tree.

Constraints:

• The number of nodes in the tree is $n$.
• $1 \leq k \leq n \leq 500$
• $0 \leq$ Node.data $\leq 10^4$