108. Convert Sorted Array to Binary Search Tree

/**
 * 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 BST(nums, 0, nums.length-1);
    }
    public TreeNode BST(int[] nums, int start, int end) {
        if(start>end) return null;
        
        int mid = (start + end)/2;
        TreeNode node = new TreeNode(nums[mid]);
        
            
        node.left = BST(nums, start, mid-1);
        node.right = BST(nums, mid + 1 , end) ;
        return node;
    }
}

//question to construct need a  number(int) to mark
//idea: get  the middle elements as the root