Sorted Array To Balanced BST

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

Balanced tree : a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1. 
Example :

Given A : [1, 2, 3]
A height balanced BST  : 

      2
    /   \
   1     3
Method:

The mid element is the root

Solution:

Time: O(n)
Space: O(n)

/**
 * Definition for binary tree
 * class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) {
 *      val = x;
 *      left=null;
 *      right=null;
 *     }
 * }
 */
public class Solution {
    // DO NOT MODIFY THE ARGUMENTS WITH "final" PREFIX. IT IS READ ONLY
    public TreeNode sortedArrayToBST(final List<Integer> A) {
        if (A.size() == 0) return null;
        int mid = A.size() / 2;
        TreeNode root = new TreeNode(A.get(mid));
        root.left = sortedArrayToBST(A.subList(0, mid));
        root.right = sortedArrayToBST(A.subList(mid + 1, A.size()));
        return root;
    }
}