Given a BST and two nodes p and q, find their lowest common ancestor. The LCA is the lowest node that has both p and q as descendants (a node can be a descendant of itself).
Example: In BST , LCA of 2 and 8 is 6. LCA of 2 and 4 is 2.
Unlike general binary trees, you can use the BST property to guide your search efficiently. Constraints: all node values are unique, both p and q exist in the tree.