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

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public TreeNode sortedArrayToBST(int[] nums) {        return subarrayToBST(nums, 0, nums.length - 1);    }    public TreeNode subarrayToBST(int[] nums, int start, int end) {        if (start > end) {            return null;        }        int mid = (start + end) / 2;        TreeNode root = new TreeNode(nums[mid]);        root.left = subarrayToBST(nums, start, mid - 1);        root.right = subarrayToBST(nums, mid + 1, end);        return root;    }}