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

Convert Sorted Array to Binary Search Tree

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode sortedArrayToBST(int[] num) {
  
        return sortedArrayToBST(num, 0, num.length-1);
    }
    
     public TreeNode sortedArrayToBST(int[] num, int lo, int hi) {
        
        TreeNode root = null;