Python Preorder + Deque Solution. Beats 98%
```\n\tdef serialize(self, root):\n        if not root:\n            return "X,"\n        return str(root.val) + "," + self.serialize(root.left) + self.serializ
```\n\tdef serialize(self, root):\n        if not root:\n            return "X,"\n        return str(root.val) + "," + self.serialize(root.left) + self.serialize(root.right)\n\n    def deserialize(self, data):\n        queue = collections.deque(data.split(\',\'))\n        return self.deserializeHelper(queue)\n    \n    def deserializeHelper(self, queue):\n        if queue:\n            node = queue.popleft()\n            if node == \'X\':\n                return None\n            new_node = TreeNode(node)\n            new_node.left = self.deserializeHelper(queue)\n            new_node.right = self.deserializeHelper(queue)\n            return new_node
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