0297: Serialize and Deserialize Binary Tree

Problem Statement

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: []

Constraints:

  • The number of nodes in the tree is in the range [0, 104].
  • -1000 <= Node.val <= 1000

Code Solution

class Solution:
    def serialize(self, root):
        res = []
        def rec(node):
            nonlocal res
            if not node:
                res.append('x')
                return
            res.append(str(node.val))
            rec(node.left)
            rec(node.right)
        rec(root)
        return " ".join(res)
    
    def deserialize(self, data):
        
        def rec(it):
            v = next(it)
            if v == 'x':
                return None
            cnode = TreeNode(
                int(v),
                rec(it),
                rec(it)
            )
            return cnode
        
        temp = iter(data.split())
        return rec(temp)