class Solution:

    def serialize(self, root):
        if not root:
            return ['#']
        return [str(root.val)] + self.serialize(root.left) + self.serialize(root.right)

    def deserialize(self, data):
        ch = data.pop(0)
        if ch == '#':
            return None
        else:
            root = TreeNode(int(ch))
        root.left = self.deserialize(data)
        root.right = self.deserialize(data)
        return root