Given an integer n, return all structurally unique binary search trees (BSTs) that can be constructed using the integers from 1 to n. Each tree should be a unique arrangement of nodes where each node contains a unique value from the set {1, 2, …, n}.
You are given the root of a binary tree. Your task is to determine whether the tree is a valid binary search tree (BST). A binary search tree is valid if for every node in the tree, the value of all nodes in its left subtree are less than its own value, and the value of all nodes in its right subtree are greater than its own value.
You are given the root of a binary search tree (BST), but two nodes in the tree were swapped by mistake. Your task is to recover the tree by swapping the two nodes back, without changing the structure of the tree.
Given the head of a singly linked list where elements are sorted in ascending order, convert it into a height-balanced binary search tree. A height-balanced binary search tree is one where the depth of the two subtrees of every node never differs by more than 1.
Given a Binary Search Tree (BST), find the lowest common ancestor (LCA) of two given nodes. The lowest common ancestor is the deepest node that is an ancestor of both nodes. An ancestor of a node is a node itself or any node in its path up to the root.
