# Convert Sorted Array to Binary Search Tree

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

For this problem, 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 the sorted array: [-10,-3,0,5,9],

One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:

0
/ \
-3   9
/   /
-10  5
``````

## Solution

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