# Serialize and Deserialize Binary Tree

### 描述​

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:

  1 / \2   3   / \  4   5

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

Example 2:

Input: root = []
Output: []

Example 3:

Input: root = [1]
Output: [1]

Example 4:

Input: root = [1,2]
Output: [1,2]

Constraints:

• The number of nodes in the tree is in the range [0, $10^4$].
• -1000 <= Node.val <= 1000

### 代码​

# Serialize and Deserialize Binary Tree# Time Complexity O(n), Space Complexity O(n)class Codec:    def serialize(self, root):        return self.serializeDFS(root, "")    def serializeDFS(self, root, string: str):        if root is None:            string += "null,"        else:            string += str(root.val) + ","            string = self.serializeDFS(root.left, string)            string = self.serializeDFS(root.right, string)        return string    def deserialize(self, data):        return self.deserializeDFS(data.split(','))    def deserializeDFS(self, l):        if l[0] == 'null':            l.pop(0)            return None        root = TreeNode(l[0])        l.pop(0)        root.left = self.deserializeDFS(l)        root.right = self.deserializeDFS(l)        return root