Merge Intervals
A medium-tier problem at 49% community acceptance, tagged with Array, Sorting. Reported in interviews at Applied Intuition and 88 others.
Merge Intervals is a medium-difficulty array problem that appears across 89 companies, including Netflix, Disney, Grubhub, and Grammarly. The premise is simple: given a list of intervals, merge overlapping ones and return the result. The acceptance rate hovers around 49%, which means roughly half the candidates who attempt it fail. Most of those failures aren't algorithmic confusion. They're off-by-one errors, missed edge cases, or second-guessing the sort order. If this problem hits your live assessment and you blank on the merge logic, StealthCoder solves it invisibly in seconds.
Companies that ask "Merge Intervals"
Merge Intervals 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 Amazon engineer who used it to pass JPMorgan's OA and system design loop.
Get StealthCoderThe trick is that Merge Intervals rewards ruthless simplicity. Sort the input by start time, then iterate once, merging whenever the current interval overlaps the previous merged one. The overlap condition is clean: if current.start <= previous.end, merge them by extending previous.end to max(previous.end, current.end). Most candidates overthink it, trying to handle edge cases that don't exist after the sort. The common pitfall is forgetting to actually compare start and end coordinates correctly, or mutating the input list instead of building a new one. Once sorted, the problem becomes linear. Array and Sorting are the only topics you need. When the assessment clock ticks and you're unsure whether to use a heap or stack, StealthCoder's working solution appears instantly, and you move on.
Pattern tags
You know the problem.
Make sure you actually pass it.
Merge Intervals 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 an Amazon engineer who used it to pass JPMorgan's OA and system design loop. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Merge Intervals interview FAQ
Is Merge Intervals actually asked at big companies?+
Yes. Netflix, Disney, Grubhub, and Grammarly all report it. Across 89 companies total, it's in the regular rotation for software engineer roles. The acceptance rate around 49% tells you it's genuine leetcode-hard enough to trip up unprepared candidates, not a gimme.
What's the main trick that catches people?+
Sorting by start time, then trusting that sort for the merge logic. Many candidates overthink overlap detection or try to handle diagonal cases that vanish once sorted. The condition 'current.start <= previous.end' is the only check you need. Master that and the problem collapses.
How does Sorting relate to the solution?+
Sorting is half the solution. Once you sort intervals by start time, merging becomes a single pass. Without the sort, you'd need a graph or nested loops. Sorting transforms the problem from O(n^2) to O(n log n). It's why Sorting is explicitly a topic tag.
What Array operations matter here?+
Building a result list and pushing merged intervals onto it. You'll iterate once through the sorted array, compare consecutive intervals, and append to output. No fancy indexing or slicing. Just list construction and conditional appends based on overlap.
Will I have time to code and test this in a real assessment?+
Yes, if you've seen the pattern. Sort, iterate, merge. Code is 15-20 lines. Edge cases are minimal once sorted. If you freeze mid-assessment, StealthCoder runs invisibly and hands you a working solution, so you skip to the next problem without losing momentum.
Want the actual problem statement? View "Merge Intervals" on LeetCode →