GitHub Software Engineer Interview Questions

A stack follows last in, first out, while a queue follows first in, first out. I would use a stack for undo history or depth-first traversal, and a queue for task processing or breadth-first traversal. The important part is choosing the structure that matches the work pattern.

I would split the problem into indexing, query handling, and result serving. The index should be built ahead of time so searches do not need to scan every repository on demand. Then I would add caching and ranking so common queries return fast and useful results.

I would decouple ingestion from processing, usually with a queue or streaming pipeline, so the front door stays responsive. Then I would shard work, store state efficiently, and make consumers idempotent so retries do not cause duplicate effects. The key is to keep the system reliable even when traffic spikes.

I would count each character in one pass, then scan the string again to find the first one with count one. That gives a simple and efficient solution with linear time. If needed, I would also mention the space trade-off depending on the character set.

A hash map stores key-value pairs and uses a hash function to find data quickly. I would say it is useful when we need fast lookup, insert, and delete operations on average. The trade-off is that collisions and memory overhead need to be handled well.