Card Range Obfuscation Part 4
Reported by candidates from Stripe's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Stripe's Card Range Obfuscation Part 4 hit the assessment circuit in November 2024, and it's a string manipulation problem with a deceptive title. You're not actually obfuscating anything for security. The real task is parsing and transforming card number ranges into a specific output format. If you've done range expansion or interval merging before, you've seen the skeleton. StealthCoder will catch the exact output format if you blank on the string construction during the live OA.
Pattern and pitfall
This problem requires you to take card ranges (likely given as start-end pairs) and output them in a normalized, obfuscated format. The trick isn't cryptography. It's understanding what 'obfuscation' means in Stripe's context: probably masking digits and representing ranges compactly. You'll need to handle edge cases around single cards vs ranges, overlapping ranges, and the exact character format they want (dashes, asterisks, partial digit reveals). The pattern leans toward string manipulation and possibly sorting or merging intervals. Common pitfall: misunderstanding the output format on first read. StealthCoder gives you the real format by scanning your screen, so you won't waste 15 minutes on invalid output.
The honest play: practice the pattern, and have StealthCoder ready for the one you didn't see coming.
You can drill Card Range Obfuscation Part 4 cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. Built for the candidate who saw this exact problem leak two days before his OA and wondered if anyone had a play.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as merge intervals. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass Stripe's OA.
Stripe reuses patterns across OAs. Built for the candidate who saw this exact problem leak two days before his OA and wondered if anyone had a play. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Card Range Obfuscation Part 4 FAQ
Is this actually about payment security or just string parsing?+
Just string parsing. Stripe's security is elsewhere. This is a coding exercise about range representation and masking syntax. The obfuscation is in the output format, not encryption.
Do I need to merge overlapping card ranges?+
Most likely, yes. If two ranges overlap or are adjacent, they should combine. This is interval merging, a classic pattern. Sort first, then iterate and merge.
What's the most common output format mistake?+
Getting the mask character wrong (asterisk vs hyphen vs X), the digit reveal pattern (first four digits? last four?), or the range separator. Read the examples three times before coding.
Can I solve this without handling overlaps?+
Not cleanly. Stripe will test overlapping ranges. You need sorting plus a single-pass merge. It's O(n log n) and standard.
How do I prepare in 48 hours if I don't have the full problem?+
Review interval merging on LeetCode (Merge Intervals). Practice string formatting in your language. Trace through a few hand-written examples with overlaps. The pattern is deterministic once you see one example output.