Design HashMap
A easy-tier problem at 66% community acceptance, tagged with Array, Hash Table, Linked List. Reported in interviews at ServiceNow and 9 others.
Design HashMap shows up in technical screens at Apple, Goldman Sachs, LinkedIn, and Nvidia, yet 34% of candidates still get stuck. You'll implement put, get, and remove on a hash table from scratch, which means collision handling, load factors, and hash function design are all fair game. This isn't a leetcode grind problem; it's testing whether you actually understand how the data structure works under the hood. If you blank on the collision strategy during a live OA, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Design HashMap"
Design HashMap 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 trap is thinking it's easy because it's labeled Easy. Most candidates write a naive approach with a fixed array and linear probing, then hit edge cases around resizing or hash distribution. The real problem is deciding between separate chaining (linked lists in each bucket) and open addressing (probe for the next empty slot). Separate chaining is cleaner and what most interviewers expect. You'll also need a reasonable hash function, though leetcode usually lets you use modulo. The acceptance rate of 66% tells you plenty of people submit something that passes the basic tests but breaks on collision patterns or boundary cases. StealthCoder is the insurance policy if you second-guess your collision logic at the 40-minute mark of a live assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Design HashMap 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 HashMap interview FAQ
Is this still asked at FAANG?+
Yes. Apple, Goldman Sachs, LinkedIn, and Nvidia all have it on their reported list. Appears across multiple team interviews, not just one silo. If you're interviewing at those companies, you need a solid answer ready.
What's the difference between separate chaining and open addressing?+
Separate chaining uses a linked list at each bucket for collisions; open addressing probes for the next empty slot. Separate chaining is simpler to implement and explain in an interview. Open addressing saves memory but is harder to get right. Most interviewers expect chaining.
Do I need to implement a resize operation?+
Not always required by the problem statement, but it's a good signal. If you have time and the interviewer doesn't explicitly forbid it, adding dynamic resizing when load factor exceeds 0.75 shows you know production-grade design. Keep it simple: double the size and rehash.
How does this relate to the Hash Table topic?+
This IS the hash table. You're building the internals. Understanding collision resolution, load factor, and hash function quality here directly applies to diagnosing hash table bottlenecks in system design and interview questions about caching.
Why is the acceptance rate only 66% if it's labeled Easy?+
Because Easy on leetcode means the brute-force passes; collision handling and edge cases trip most people. Candidates often forget to handle None returns, collisions on the same key, or don't test their hash function distribution. Drill the hidden cases.
Want the actual problem statement? View "Design HashMap" on LeetCode →