108. Convert Sorted Array to Binary Search Tree

EASY

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.

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def sortedArrayToBST(self, nums: List[int]) -> Optional[TreeNode]:
        length = len(nums)
        if length == 0:
            return None
        index = length // 2
        root = TreeNode(nums[index])
        root.left = self.sortedArrayToBST(nums[:index])
        root.right = self.sortedArrayToBST(nums[index+1:])
        return root