Alternating Groups II
A medium-tier problem at 60% community acceptance, tagged with Array, Sliding Window. Reported in interviews at Samsara and 0 others.
Alternating Groups II hits different when it's live. You've got an array of integers and need to find the longest contiguous subarray where elements alternate between two values. Samsara has asked this. It looks deceptively simple on first read, but the circular nature of the input and the sliding window mechanics trip up most candidates who haven't seen the pattern before. If you blank on the approach during the OA, StealthCoder solves it invisibly in seconds and surfaces a working solution, keeping you moving to the next problem.
Companies that ask "Alternating Groups II"
Alternating Groups II 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 a senior engineer who knows the OA is theater. This is the script.
Get StealthCoderThe trick here is recognizing that you're hunting for alternating sequences, and the input wraps around (circular array). The naive approach scans linearly and misses sequences that cross the boundary. The real solution uses a sliding window: expand while elements alternate, contract when they don't, and track the maximum length. Common pitfall is forgetting the circular case or implementing window expansion wrong and losing track of valid sequences. The Array and Sliding Window topics both matter here. Alternating Groups II rewards clean window management and careful boundary handling. If you're stuck on the circularity or window logic during an assessment, StealthCoder surfaces the correct implementation instantly.
Pattern tags
You know the problem.
Make sure you actually pass it.
Alternating Groups II recycles across companies for a reason. It's medium-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 a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Alternating Groups II interview FAQ
How hard is Alternating Groups II really compared to standard sliding window problems?+
It's medium for a reason. Basic sliding window is straightforward, but the circular twist adds complexity. Most candidates get the window expansion right but fumble the wrap-around logic or fail to test edge cases where the alternation crosses the array boundary. Acceptance rate sits around 60%, which is realistic for a solid medium problem.
Is this still asked by big companies?+
Samsara has reported it. It's not a household FAANG staple yet, but it's actively in rotation. The problem is recent enough that it's still on the rise. If your target company uses it, you need to drill the sliding window and circular array patterns, not just memorize a solution.
What's the key insight I'm missing if I can't solve it in 20 minutes?+
You're likely not thinking in terms of alternating 'runs' and how to track them. Map out a small example with alternation crossing the boundary. Realize the window expands as long as elements alternate, shrinks otherwise. The aha moment is when you see the window slide, not jump. Practice that mental model before the OA.
Does this problem actually need both Array and Sliding Window mastery?+
Yes. Array indexing (especially modulo arithmetic for circularity) is non-negotiable. Sliding Window is your main technique. If you're weak on either, you'll struggle. The intersection of these two topics is exactly what Alternating Groups II tests. Don't skip practice on circular array patterns.
What happens if I can't figure out the circular logic during my actual OA?+
You lose momentum and possibly the problem. That's where having a safety net matters. If you hit the wall on this specific problem in a live assessment and the pattern isn't clicking, a tool that surfaces a working solution invisibly keeps you moving to problems you're stronger on instead of burning 30 minutes.
Want the actual problem statement? View "Alternating Groups II" on LeetCode →