python recursion constant space beats 98% short solution
\nclass Solution:\n    def connect(self, root: \'Node\') -> \'Node\':\n        if not root or not root.left:\n            return root\n        \n        root.le
```\nclass Solution:\n    def connect(self, root: \'Node\') -> \'Node\':\n        if not root or not root.left:\n            return root\n        \n        root.left.next = root.right\n        \n        if root.next:\n            root.right.next = root.next.left\n        \n        self.connect(root.left)\n        self.connect(root.right)\n        return root\n```
['Python', 'Python3']