How do you serialize and deserialize a Binary Tree?

0-2 years experience

1. 1Write a function to serialize a binary tree to a string using preorder traversal with '#' for nulls. How would you then deserialize it back?
2. 2If you have a tree where some nodes have only left children, what will your serialization output look like, and how does your deserialization handle it?
3. 3What would happen if you forget to include a delimiter between node values in your serialized string?

2-5 years experience

1. 1We need to store user session trees in a Redis cache. Which serialization format would you pick for a binary tree and why?
2. 2During a recent release, deserialization started throwing an IndexOutOfBoundsException for certain trees. Walk me through how you'd debug the issue.
3. 3If the tree can be very deep (depth > 10,000), how would you modify your serialization/deserialization to avoid stack overflow?

5-8 years experience

1. 1Our service exchanges binary trees over the network at high QPS. Discuss the trade‑offs between a compact binary format vs a human‑readable text format for serialization.
2. 2Design a version‑tolerant serialization scheme that allows adding new fields to tree nodes without breaking older services.
3. 3How would you benchmark and optimise the throughput of your tree serialization pipeline under 1 GB/s traffic?

8+ years experience

1. 1We are migrating a legacy monolith that uses a custom pointer‑based tree representation to a microservice architecture. How would you plan the migration of tree persistence while ensuring backward compatibility?
2. 2Across multiple teams, different languages need to share the same tree data. What architecture would you propose for a language‑agnostic serialization contract, and how would you govern its evolution?
3. 3If we need to support incremental updates (diffs) to large trees rather than full serialization each time, what design would you recommend?