https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.
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.
1 <= nums.length <= 10^4
-10^4 <= nums[i] <= 10^4
nums is sorted in a strictly increasing order.
PS: 这一题也可以结合无顺序作为考点，不过难度不大。