Neetcode: Kth Smallest Integer in BST

Instructions

Given the root of a binary search tree, and an integer k, return the kth smallest value (1-indexed) in the tree.

A binary search tree satisfies the following constraints:

• The left subtree of every node contains only nodes with keys less than the node's key.
• The right subtree of every node contains only nodes with keys greater than the node's key.
• Both the left and right subtrees are also binary search trees.

Example 1:

Input: root = [2,1,3], k = 1

Output: 1

Example 2:

Input: root = [4,3,5,2,null], k = 4

Output: 5

Constraints:

• 1 <= k <= The number of nodes in the tree <= 1000
• 0 <= Node.val <= 1000