https://www.hackerrank.com/challenges/tree-height-of-a-binary-tree/problem
The height of a binary tree is the number of edges between the tree's root and its furthest leaf. The Height of binary tree with single node is taken as zero.
Input Format:
The first line contains an integer n, the number of nodes in the tree.
Next line contains n space separated integer where i integer denotes node[i].data.
In a binary search tree, all nodes on the left branch of a node are less than the node value. All values on the right branch are greater than the node value.