297. Serialize and Deserialize Binary Tree

https://leetcode.com/problems/serialize-and-deserialize-binary-tree

Python

class Codec:
    EMPTY_CHAR = "-"
    def serialize(self, root: TreeNode) -> str:
        """Encodes a tree to a single string.

        :type root: TreeNode
        :rtype: str
        """

        result = self._serialize(root, [])

        return " ".join(result) if result else ""

    def _serialize(self, node: TreeNode, holder: list) -> list:
        if not node:
            holder.append(self.EMPTY_CHAR)
            return

        holder.append(str(node.val))
        self._serialize(node.left, holder)
        self._serialize(node.right, holder)

        return holder


    def deserialize(self, data: str) -> TreeNode:
        """Decodes your encoded data to tree.

        :type data: str
        :rtype: TreeNode
        """
        if not data:
            return

        vals = data.split(' ')[::-1]

        return self._deserialize(vals)

    def _deserialize(self, vals: list) -> TreeNode:
        val = vals.pop()

        if val == self.EMPTY_CHAR:
            return None

        node = TreeNode(int(val))
        node.left = self._deserialize(vals)
        node.right = self._deserialize(vals)
        return node


# Your Codec object will be instantiated and called as such:
# ser = Codec()
# deser = Codec()
# ans = deser.deserialize(ser.serialize(root))