new_contents: # https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
  from TreeNode import TreeNode
  class Solution(object):
      def sortedArrayToBST(self, nums):
          if not nums : return None
          n = len(nums)
          if n == 1:
              return TreeNode(nums[0])
          mid = TreeNode(nums[n // 2])
          mid.left = self.sortedArrayToBST(nums[:n // 2])
          mid.right = self.sortedArrayToBST(nums[n // 2 + 1:])
          return mid
subject: convert sorted array to binary search tree