Given a binary tree, check whether it’s a binary search tree or not.
I cheated a little in this question because I didn’t remember what a binary search tree is. After checking wikipedia I found the characteristic of a BST:
– The left subtree of a node contains only nodes with keys less than the node’s key.
– The right subtree of a node contains only nodes with keys greater than the node’s key.
– The left and right subtree each must also be a binary search tree.
– Each node can have up to two successor nodes.
– There must be no duplicate nodes.