Serialize and Deserialize a Binary Tree

Last updated: June 17, 2026

Quick Overview

Design an algorithm to serialize a binary tree to a string and deserialize it back. Tests tree traversal and string parsing skills, a recurring Google question.

Google
Coding & Algorithms
Software Engineer
Google
June 17, 2026
Software Engineer
Onsite
Coding & Algorithms
Hard

122

0

339 solved


Design an algorithm to serialize a binary tree to a string and deserialize it back. Tests tree traversal and string parsing skills, a recurring Google question.

How to Approach This
  1. Clarify input constraints and edge cases before writing code.
  2. Walk through your approach verbally and confirm with the interviewer before coding.
  3. Start with a brute force solution, then optimize. Mention time and space complexity.
  4. Test your solution with examples, including edge cases like empty input or duplicates.
  5. Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
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Problem Analysis

The problem at hand requires serializing a binary tree into a string format and then deserializing it back to reconstruct the original tree. The key pattern that applies here is the use of depth-first...

Approach
  1. Serialization: We will use a pre-order traversal (node -> left -> right) to serialize the tree. During traversal, we will append the value of each node to a list, using a placeholder (e.g., 'nu...

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