Convert Sorted Array to Binary Search Tree

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

Solution

/**
 * 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) {
        if (nums == null || nums.length == 0) return null;
        return sortedArrayToBST(nums, 0, nums.length - 1);
    }

    public TreeNode sortedArrayToBST(int[] nums, int start, int end) {
        if (start > end) {
            return null;
        }

        int rootPosition = start + (end - start) / 2;
        TreeNode root = new TreeNode(nums[rootPosition]);
        root.left = sortedArrayToBST(nums, start, rootPosition - 1);
        root.right = sortedArrayToBST(nums, rootPosition + 1, end);

        return root;

    }
}