Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

Clarification: The input/output format is the same as how LeetCode serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Example 1:

Input: root = [1,2,3,null,null,4,5]
Output: [1,2,3,null,null,4,5]

Example 2:

Input: root = []
Output: []

class Codec:
    def serialize(self, root):
        res = []

        def dfs(node):
            if not node:
                res.append("N")
                return
            res.append(str(node.val))
            dfs(node.left)
            dfs(node.right)

        dfs(root)
        ans = ",".join(res)
        return ans

    def deserialize(self, data):
        self.i = 0
        data = data.split(',')

        def dfs():
            if data[self.i] == "N":
                self.i += 1
                return None
            else:
                node = TreeNode(int(data[self.i]))
                self.i += 1
                node.left = dfs()
                node.right = dfs()
                return node

        return dfs()