Count Ways to Group Overlapping Ranges
A medium-tier problem at 38% community acceptance, tagged with Array, Sorting. Reported in interviews at IBM and 0 others.
Count Ways to Group Overlapping Ranges is a medium-difficulty problem that shows up in IBM's assessments. With a 38% acceptance rate, it's tricky enough that most candidates either nail the sorting insight or crash into the weeds. The problem wants you to partition ranges into groups where ranges in the same group overlap or chain together. You need to count how many distinct valid groupings exist. It's not a problem you drill casually, and if it hits your live OA cold, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Count Ways to Group Overlapping Ranges"
Count Ways to Group Overlapping 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 an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code.
Get StealthCoderThe trick is recognizing that overlapping ranges must live in the same group, so you first sort by start position, then merge overlaps into connected components. Once you've identified which ranges belong together, the counting step is combinatorial: if you have isolated groups, each group's ranges can be partitioned independently, and the total count is the product of counts across all groups. Most candidates either miss the sorting prerequisite or confuse 'overlapping' with 'adjacent,' leading to wrong merges. The Array and Sorting topics are table stakes here. If you haven't drilled the pattern of merging intervals and then counting combinations, StealthCoder is the hedge for the live assessment when you hit this specific problem and feel the clock pressure.
Pattern tags
You know the problem.
Make sure you actually pass it.
Count Ways to Group Overlapping Ranges 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 realized the OA tests how well you memorized 200 problems, not how well you code. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Count Ways to Group Overlapping Ranges interview FAQ
How hard is this problem really compared to other medium coding problems?+
The 38% acceptance rate signals it's on the harder end of medium. Most people pass interval sorting, but the combinatorial counting step trips them up. It requires both a sorting pattern and a sense for how grouping affects the final count. Not something to underestimate.
Does IBM ask this problem frequently in their assessments?+
IBM has reported asking it. With only one company in the data and a low acceptance rate, it's likely a harder screening problem for them, not a warm-up. If you're interviewing there, don't assume they'll skip it.
What's the algorithmic trick I need to know?+
Sort ranges by start position, then greedily merge overlapping ones into groups. Each group becomes an independent subproblem. The final answer is the product of group counts because each group's partition choice multiplies with the others. Missing the product rule is common.
How do Array and Sorting topics connect to the solution?+
Sorting is mandatory to identify which ranges can overlap (you can't spot overlaps in unsorted data). Array skills handle the merging and grouping logic. Both topics are foundational; neither is optional here.
What's the most common mistake candidates make on this problem?+
Sorting correctly but then misunderstanding how to count partitions. Candidates often treat overlapping ranges as a graph and try to enumerate all valid colorings, missing the cleaner product formula. Reading the problem carefully for what 'valid grouping' means is critical.
Want the actual problem statement? View "Count Ways to Group Overlapping Ranges" on LeetCode →