Leetcode Convert Sorted Array to Binary Search Tree

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

Difficulty: Medium

/** * 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 helper(int[] nums, int begin, int end){        if(end < begin) return null;        if(begin == end) return (new TreeNode(nums[begin]));        if(end - begin == 1){            TreeNode root = new TreeNode(nums[begin]);            root.right = helper(nums, end, end);            return root;        }        int mid = (end - begin)/2 + begin;        TreeNode root = new TreeNode(nums[mid]);        root.left = helper(nums, begin, mid - 1);        root.right = helper(nums, mid + 1, end);        return root;            }    public TreeNode sortedArrayToBST(int[] nums) {        if(nums.length == 0) return null;        return helper(nums, 0, nums.length - 1);    }}