public Node sortedArrayToBST(int[] nums) {
        return toBST(nums, 0, nums.length - 1);
    }
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