In-place merge two height-balanced BSTs

Given two height-balanced binary search trees, in-place merge them into a single balanced binary search tree. For each node of a height-balanced tree, the difference between its left and right subtree height is at most 1.

Determine whether a BST is skewed from its preorder traversal

Given an array representing the preorder traversal of a BST, determine whether it represents a skewed BST or not. In a skewed BST, each node’s descendants are either smaller or larger than the node itself.