Introduction - If you have any usage issues, please Google them yourself
All empty tree is a binary search tree.
A binary tree is not empty, the root R is a binary search tree if:
• In case of left subtree, the root R must be greater than the maximum value
stored in the left subtree, and that the left subtree is a binary tree
search.
• If you have the right subtree, the root R must be less than the minimum
stored in the right subtree, and the right subtree is a binary tree
search.