Divide Array in Sets of K Consecutive Numbers
A medium-tier problem at 59% community acceptance, tagged with Array, Hash Table, Greedy. Reported in interviews at Waymo and 0 others.
You're given an array and a number K. You need to split the entire array into groups where each group contains exactly K consecutive integers. No leftovers. No gaps. It sounds simple until you realize the greedy approach most candidates try first fails silently. The problem appears in Waymo interviews and has a 59% acceptance rate, which means half the candidates who attempt it leave it on the table. If this hits your live assessment and you're stuck on why your straightforward solution doesn't work, StealthCoder runs invisibly during the screen share and surfaces the correct approach in seconds.
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Divide Array in Sets of K Consecutive Numbers 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. Made for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trap is assuming you can just sort and iterate. You can't. The real issue: once you pick a starting number, you commit to building K consecutive numbers from it. If those consecutive numbers don't exist in your array, you fail. The solution requires a greedy strategy combined with a hash table to track availability. You sort the array, iterate through candidates for the start of each group in ascending order, and for each valid start, you consume K consecutive numbers. If any number in the sequence is missing or already used, the entire partition is impossible. Hash tables let you verify membership and decrement counts in O(1). Most candidates either skip the sorting step or try to be clever with grouping logic that doesn't respect the "consecutive" constraint. When you hit this live, the time cost of backtracking from a broken approach is brutal. StealthCoder hedges that exact moment by showing you the hash table plus greedy iteration pattern.
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Divide Array in Sets of K Consecutive Numbers 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. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Divide Array in Sets of K Consecutive Numbers interview FAQ
Is this problem asking for a specific ordering of groups?+
No. The groups themselves don't have an output order. What matters is that each group contains exactly K consecutive integers and every element in the input belongs to exactly one group. If such a partition exists, any valid output is correct.
Why does sorting the array matter here?+
Sorting lets you iterate through potential group starts in ascending order. The greedy choice is to always start a new group with the smallest remaining number. This guarantees you don't miss a valid partition that exists. Without sorting, you'd chase numbers randomly and hit dead ends.
What's the role of the hash table?+
It tracks available numbers and their counts. When you pick a starting number, you check the hash table to confirm the next K-1 consecutive numbers exist. As you use numbers, you decrement their counts. This is O(1) per lookup and update, vastly faster than searching the array repeatedly.
Can I solve this without sorting?+
Technically, you could use a hash table only, but you'd lose the greedy guarantee. Sorting makes the greedy strategy work and keeps the code cleaner. Most interviewers expect the sorted plus hash table approach. It's O(n log n) time, which is standard for this problem class.
How hard is this compared to other medium array problems?+
The greedy insight isn't obvious. Many candidates solve easy array problems fine but stumble here because the naive sort-and-iterate won't work. Waymo asking it signals they want to see if you can catch your own mistake and correct to the hash table approach mid-interview.
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