How much DSA do interviewers expect you to memorize?

Know the core patterns well enough to recognize when they fit and explain why. For example, be ready to reason through a tree traversal, a breadth-first search, or reversing a linked list. You probably don’t need every line of library-quality code memorized, but you should be able to work out a basic version under interview conditions.

There’s a difference between being able to explain an algorithm and reciting an implementation. A course or written exam may expect you to reproduce particular details, including how a specific tree stays balanced. In an interview, the emphasis can be more on choosing an approach, discussing its time and space costs, and adapting it to the problem. The company and interview format matter a lot.

Don’t spend all your prep time on AVL rotations unless the role or interview guide points you there. Get comfortable with arrays, hash tables, stacks, queues, linked lists, trees, graphs, sorting, and common searches. Practice coding a few fundamentals from scratch, then focus on explaining edge cases and complexity as you go.

For a senior role, your practical judgment is part of the picture, but it may not replace the coding screen. Try to find out what the interview actually includes. Some teams give puzzle-like problems, while others ask you to choose a structure for a concrete use case and explain the tradeoffs. Preparing for the specific format beats trying to memorize every algorithm you’ve ever heard of.