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

# Definition for a binary tree node.class TreeNode:    def __init__(self, x):        self.val = x        self.left = None        self.right = Noneclass Solution:    def sortedArrayToBST(self, nums):        """        :type nums: List[int]        :rtype: TreeNode        """        if len(nums)<1:            return None        index = len(nums)//2        root = TreeNode(nums[index])        root.left = self.sortedArrayToBST(nums[:index])        root.right = self.sortedArrayToBST(nums[index+1:])        return root