Design Skiplist
A hard-tier problem at 58% community acceptance, tagged with Linked List, Design. Reported in interviews at eBay and 2 others.
Skip list problems sit at the intersection of linked lists and probabilistic data structures. You'll see this at eBay, X, and Pure Storage, and it's a legitimate hard problem that most candidates haven't built before. The catch: the naive approach (a flat linked list) fails the performance requirements immediately. You need to understand how to layer nodes probabilistically to achieve O(log n) search, insert, and delete. If you hit this cold in an assessment and don't know the skip list pattern, StealthCoder runs invisibly and surfaces a working implementation in seconds.
Companies that ask "Design Skiplist"
Design Skiplist 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. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoderA skip list uses parallel linked lists at different levels to skip ahead during traversal, trading space for speed. The trick is assigning each new node a random height and threading it through the appropriate levels. Most candidates either try to build a standard linked list (too slow) or overthink the randomization logic. The real complexity lies in maintaining invariants during deletion and handling the head sentinel correctly. Understanding probability and how levels connect is non-negotiable. When you're stuck mid-interview and your solution times out, StealthCoder hedges that wall by delivering the correct structure and node-threading logic so you can move forward.
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Design Skiplist recycles across companies for a reason. It's hard-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. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Design Skiplist interview FAQ
Is skip list design really asked at top companies?+
Yes. eBay, X, and Pure Storage all report this problem. It's less common than hash maps or trees but appears consistently in system design and advanced data structure rounds, especially at storage and infrastructure companies.
What's the actual trick I'm missing?+
Random node heights and level indexing. Most candidates fail because they treat skip lists like balanced trees. The insight: randomly assign height when inserting, then thread the node through all levels it belongs to. Deletion requires updating forward pointers at each level the node occupies.
How does skip list relate to linked lists?+
Skip lists are linked lists with extra forward pointers at multiple levels. If you nail linked list pointer manipulation, skip lists are the next step up. They inherit insertion and deletion patterns but add the complexity of level management and probability.
What's the time complexity I need to hit?+
Search, insert, and delete should all be O(log n) on average. A flat linked list gives you O(n), which fails immediately. The probabilistic leveling gets you the logarithmic guarantee without explicit balancing logic.
Will I need to code the random height generator?+
Almost certainly. Most solutions ask you to generate a random level for each node (usually capped at a max level like 16). This is short code but critical. If you skip it or hard-code heights, your solution won't reflect actual skip list behavior.
Want the actual problem statement? View "Design Skiplist" on LeetCode →