Binary Search Tree (BST):
Insert: insert new node into BST.
Search: find data node inside BST.
Tree Depth: measure maximum depth of BST.
Validity of BST: check validity of BST.
Lowest Common Ancestor: find the lowest common ancestor of two nodes.
Balanced BST: is BST balanced/unbalanced.
HINT: A balanced tree is defined to be one such that the heights of the two sub-trees of any node never differ more than one.
Path to Node: Mapping route path to a BST node.