Leetcode 297. Serialize and Deserialize Binary Tree

Problem

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.

Algorithm

Use dfs to serialize and deserialize the tree.

Code

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Codec:

    def serialize(self, root):
        """Encodes a tree to a single string.
        
        :type root: TreeNode
        :rtype: str
        """
        def dfs(node):
            if not node:
                ans.append("#")
                return
            ans.append(str(node.val))
            dfs(node.left)
            dfs(node.right)
        
        ans = []
        dfs(root)
        return ",".join(ans)

    def deserialize(self, data):
        """Decodes your encoded data to tree.
        
        :type data: str
        :rtype: TreeNode
        """
        def dfs():
            nonlocal index
            index = index + 1
            val = vals[index]
            if val == "#":
                return None
            node = TreeNode(int(val))
            node.left = dfs()
            node.right = dfs()
            return node
        
        vals = data.split(",")
        index = -1
        return dfs()
        

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