private Node toBST(int[] nums, int low, int high) {
        if (low > high) {
            return null;
        }
        int mid = (low + high)/2;
        Node n = Node.newNode(nums[mid]);
        n.left = toBST(nums, low, mid - 1);
        n.right = toBST(nums, mid + 1, high);
        return n;
    }
Date 10/06/2016
@author Tushar Roy

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

Time complexity O(n)

Reference
https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
src/com/interview/tree/SortedArrayToBST.java