Smallest and fastest Python solution. 147 ms
class Solution:\n\n        def sortedArrayToBST(self, num):\n\n            if not num:\n                return None\n\n            median  = len(num)/2\n       
    class Solution:\n\n        def sortedArrayToBST(self, num):\n\n            if not num:\n                return None\n\n            median  = len(num)/2\n            new_node = TreeNode(num[median])\n    \n            new_node.left = self.sortedArrayToBST(num[:median])\n            new_node.right = self.sortedArrayToBST(num[median+1:])\n            \n            return new_node
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