Given an integer array `nums` where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.

A height-balanced binary tree is a binary tree in which the depth of the two subtrees of every node never differs by more than one.

Example 1:

    Input: nums = [-10,-3,0,5,9]
    Output: [0,-3,9,-10,null,5]
    Explanation: [0,-10,5,null,-3,null,9] is also accepted:

Example 2:

    Input: nums = [1,3]
    Output: [3,1]
    Explanation: [1,null,3] and [3,1] are both height-balanced BSTs.

Constraints:

- `1 <= nums.length <= 104`
- `-104 <= nums[i] <= 104`
- `nums` is sorted in a strictly increasing order.