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# Runtime: 372 ms (Top 18.39%) | Memory: 20.4 MB (Top 30.28%)
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class Codec:
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    def serialize(self, root):
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        if not root:
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            return "N"
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        left = self.serialize(root.left)
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        right = self.serialize(root.right)
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        return ",".join([str(root.val), left, right])
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    def deserialize(self, data):
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        data = data.split(",")
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        root = self.buildTree(data)
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        return root
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    def buildTree(self, data):
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        val = data.pop(0)
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        if val == "N":
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            return None
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        node = TreeNode(val)
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        node.left = self.buildTree(data)
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        node.right = self.buildTree(data)
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        return node