Smallest Set Covering Intervals
Reported by candidates from Snowflake's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Snowflake asked this in January 2024, and it's a greedy interval problem that trips up candidates who default to brute force. You're given a set of intervals and need to find the smallest subset that covers a target range. The trick is that a greedy approach works here: sort by start position, then always pick the interval that extends furthest right from your current position. If you blank on the greedy strategy during the OA, StealthCoder reads the problem and feeds you the pattern in real time.
Pattern and pitfall
This is a classic greedy problem disguised as a set cover question. The algorithm: sort intervals by start position (and by end position descending as tiebreaker), then iterate through and always select the interval that reaches furthest right. The common trap is trying to solve it with dynamic programming or backtracking when greedy is both correct and faster. The insight is that once you're at a position, there's never a reason to pick an interval that doesn't extend you as far as possible. During the live OA, if the pattern doesn't click, StealthCoder can outline the greedy approach so you don't waste time on wrong paths.
StealthCoder is the hedge for the one pattern you didn't drill. It runs invisibly during the screen share.
You can drill Smallest Set Covering Intervals 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. If you're reading this with an OA window open, you're who this was built for.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as video stitching. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass Snowflake's OA.
Snowflake reuses patterns across OAs. If you're reading this with an OA window open, you're who this was built for. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Smallest Set Covering Intervals FAQ
Is this a standard LeetCode-style greedy problem?+
Yes. It's structurally similar to 'Video Stitching' and 'Jump Game II.' The core pattern is the same: sort, then iterate left-to-right, always picking the option that extends you furthest. Once you see it, the code is 10-15 lines.
What's the most common mistake candidates make?+
Overthinking it as a DP or optimization problem. Greedy works. Sort by start, iterate, pick the interval with max end from your current position. Don't code until you're sure the greedy choice is optimal.
How do I verify my greedy solution is correct?+
Prove that picking the interval with the largest right endpoint at each step never closes off a better solution. If greedy fails a test case, you likely have a sorting or boundary condition bug, not a logic flaw.
What edge cases should I test before submitting?+
Intervals that don't fully cover the target range (return failure or empty set), overlapping intervals, intervals that start before the target, and a single interval that covers everything. Handle off-by-one on the boundary.
Can I solve this in under 20 minutes?+
Yes, if you recognize the greedy pattern immediately. Sort (O(n log n)), then linear scan. Total under 30 lines. The time limit is usually generous on this type of problem.