Design HashSet
A easy-tier problem at 67% community acceptance, tagged with Array, Hash Table, Linked List. Reported in interviews at Wix and 0 others.
Design HashSet is easy-rated but carries weight in system design rounds at companies like Wix. You're not implementing a hashtable from scratch often, but when you are, candidates blank on collision handling and load factors. The acceptance rate sits at 67%, which means a third of people fail it live, usually on edge cases around rehashing or the actual storage mechanism. This problem forces you to think about what a hashtable actually is instead of just calling a library. If you hit this during your assessment and freeze on how to handle collisions, StealthCoder runs invisibly and surfaces a working implementation in seconds.
Companies that ask "Design HashSet"
Design HashSet is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trick here is that 'easy' doesn't mean straightforward. You need to decide: do you use separate chaining with linked lists, or open addressing with probing. Most candidates default to chaining because it's simpler to reason about, but they botch the implementation by not actually building the array of buckets correctly. The real pitfall is treating this like a coding problem when it's actually a design problem. You have to justify your collision strategy and explain why your load factor matters. The topics Array, Hash Table, Linked List, and Hash Function aren't just labels; they're your roadmap. If you choose chaining, you'll use Array plus Linked List. If you choose probing, you only need Array. Most people pick the first path and then forget to implement the linked list correctly. When the problem asks you to add, remove, and contains operations, each one needs to hash the key, find the bucket, then navigate the collision structure. StealthCoder hedges the moment you realize you picked a strategy but can't code it cleanly.
Pattern tags
You know the problem.
Make sure you actually pass it.
Design HashSet recycles across companies for a reason. It's easy-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Design HashSet interview FAQ
Is Design HashSet really only easy difficulty?+
Officially yes, but the 67% acceptance rate suggests otherwise. The design and collision-handling logic trip up mid-level engineers who've never built one. If you're a systems engineer or have strong fundamentals, it's straightforward. Otherwise, it's a hidden medium.
What's the most common mistake on this problem?+
Implementing the hash function correctly but then forgetting to actually build the array of buckets, or building it wrong. Candidates also over-engineer the load factor and rehashing logic when the problem just wants add, remove, and contains. Keep it minimal.
Should I use chaining or open addressing?+
Chaining with a linked list is more forgiving and easier to explain in an interview. Open addressing is clever but requires more careful probing strategy. Chaining aligns with the topics listed: Array, Hash Table, and Linked List are all needed. Stick with chaining unless the interviewer specifically pushes you toward probing.
Does Wix ask this, and what variant do they prefer?+
Wix is the only company reported to ask this. They likely care about your design reasoning more than the code itself. Be ready to discuss bucket size, collision strategy, and when you'd rehash. The implementation just proves you understand the concept.
What should I actually code in the interview?+
Implement add, remove, and contains. Use an array of size around 1000 as your bucket count. For each operation, hash the key modulo the bucket size, then search or insert in that bucket's linked list. Don't overcomplicate. Clarity over perfection.
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