[Leetcode] 0297. Serialize and Deserialize Binary Tree

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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, 10 ⁴ ].
-1000 <= Node.val <= 1000

Table of contents

Python

				
					# time complexity: O(n) # space complexity: O(h) from collections import deque from typing import Optional class Codec: def serialize(self, root: Optional[TreeNode]) -> str: if not root: return '' queue = deque([root]) result = [] while queue: node = queue.popleft() if node: result.append(str(node.val)) queue.extend([node.left, node.right]) else: result.append('None') return ','.join(result) def deserialize(self, data: str) -> Optional[TreeNode]: if not data: return None dataList = data.split(',') root = TreeNode(int(dataList[0])) queue = deque([root]) i = 1 while queue and i < len(dataList): node = queue.popleft() leftVal, rightVal = dataList[i], dataList[i+1] if i + 1 < len(dataList) else 'None' if leftVal != 'None': node.left = TreeNode(int(leftVal)) queue.append(node.left) if rightVal != 'None': node.right = TreeNode(int(rightVal)) queue.append(node.right) i += 2 return root # Your Codec object will be instantiated and called as such: root = TreeNode(1) root.left = TreeNode(2) root.right = TreeNode(5) root.left.left = TreeNode(3) root.left.right = TreeNode(4) ser = Codec() deser = Codec() tree = ser.serialize(root) print(tree) # '1,2,5,3,4,None,None,None,None,None,None,' ans = deser.deserialize(tree) print(ans.val) # 1 print(ans.left.val) # 2 print(ans.right.val) # 5 print(ans.left.left.val) # 3 print(ans.left.right.val) # 4

Python

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