Convert Sorted Array to Binary Search Tree

lcpy gen -n 108   # by problem number
lcpy gen -s convert_sorted_array_to_binary_search_tree   # by problem name

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:

![Alt](https://assets.leetcode.com/uploads/2021/02/18/btree2.jpg)

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

from leetcode_py import TreeNode


class Solution:
    # Time: O(n) — each element becomes one node
    # Space: O(log n) recursion stack for a balanced build
    def sorted_array_to_bst(self, nums: list[int]) -> TreeNode[int] | None:
        def build(left: int, right: int) -> TreeNode[int] | None:
            if left > right:
                return None
            mid = (left + right) // 2
            node = TreeNode[int](nums[mid])
            node.left = build(left, mid - 1)
            node.right = build(mid + 1, right)
            return node

        return build(0, len(nums) - 1)