Summary Ranges
A easy-tier problem at 53% community acceptance, tagged with Array. Reported in interviews at Yandex and 4 others.
Summary Ranges is deceptively simple. You're given an array of integers and need to group consecutive numbers into ranges, returning them as strings like "1->3" or "5". It sounds straightforward, but candidates blank on the edge cases: single numbers that aren't ranges, gaps in sequences, and off-by-one errors in boundary detection. Google, Netflix, and Bloomberg use this to filter out people who rush. It has a 53% acceptance rate, which means half the people who attempt it fail under pressure. If you hit this on an assessment and freeze on the grouping logic, StealthCoder solves it invisible to the proctor in seconds.
Companies that ask "Summary Ranges"
Summary Ranges 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 is tracking a range start and iterating once through the array, comparing each element to the previous. When you detect a gap (current - previous > 1), you close the range, format it, and start a new one. Common failures: forgetting to handle the final range after the loop ends, mishandling single-element ranges, or using >= instead of > when checking gaps. The Array topic is core here because you're not sorting or searching, just scanning linearly and building output strings. Most people over-engineer it with nested loops or multiple passes. If you haven't drilled this pattern and it appears in your live OA, StealthCoder gives you a working solution fast enough to move on.
Pattern tags
You know the problem.
Make sure you actually pass it.
Summary Ranges 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. Built by a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Summary Ranges interview FAQ
How hard is Summary Ranges really?+
It's marked Easy but the 53% acceptance rate tells you the truth: candidates get tripped up on edge cases and string formatting under time pressure. The algorithm is linear and simple. The difficulty is in not making mistakes, not in conceptual complexity.
Is this still asked at top companies?+
Yes. Google, Netflix, and Bloomberg are confirmed recent askers. It's popular at tech companies because it's quick to grade, easy to validate, and exposes sloppy thinking fast. You'll see it in phone screens and online assessments.
What's the most common mistake?+
Forgetting to append the final range after the loop terminates. Candidates build the range correctly for all interior gaps, then submit with the last group missing. Test with an array like [1,2,3] and trace the output manually.
Does this problem need preprocessing or sorting?+
No. The input is already sorted (per the problem statement). You scan once, track the start and end of each range, and output when you hit a gap or the end of the array. No sorting, no extra structure needed.
How does Summary Ranges relate to the Array topic?+
It's a pure linear scan. You're not searching, hashing, or partitioning. You iterate once, maintain state (range start/end), and output strings. It tests whether you can handle iteration and state transitions cleanly.
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