Make a Positive Array
A medium-tier problem at 38% community acceptance, tagged with Array, Greedy, Prefix Sum. Reported in interviews at UKG and 0 others.
Make a Positive Array is a medium-difficulty problem that hits on array transformation and prefix logic. UKG has asked it. The 38% acceptance rate signals it's not a straightforward iteration task. Most candidates who fail it either miss the greedy pattern or try to solve it greedily without thinking through prefix constraints. If you blank on the trick during your OA, StealthCoder runs invisibly and surfaces the working solution in seconds.
Companies that ask "Make a Positive Array"
Make a Positive Array 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 because the OA filter rejects engineers who'd pass the on-site. That's a broken filter. This is the workaround.
Get StealthCoderThe problem requires you to transform an array so all elements are positive, usually by incrementing subarrays or similar operations. The catch is minimizing steps or cost. The greedy instinct is often wrong because changing a prefix affects everything downstream. The real pattern involves prefix sums and working backwards or using a sweep to track cumulative changes. Most failed attempts come from trying to patch elements left-to-right without accounting for earlier decisions. This is where the prefix sum topic becomes crucial. If you hit this live and haven't drilled the pattern, StealthCoder gives you the correct greedy or DP framing and working code.
Pattern tags
You know the problem.
Make sure you actually pass it.
Make a Positive Array 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 because the OA filter rejects engineers who'd pass the on-site. That's a broken filter. This is the workaround. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Make a Positive Array interview FAQ
Is Make a Positive Array still asked at tech companies?+
Yes. UKG has reported asking it. It's not a common Leetcode problem, which means fewer candidates have seen it and more rely on pattern recognition in the moment. That scarcity makes it a screening filter.
What's the common mistake on this problem?+
Greedy left-to-right fixes without tracking prefix impact. Candidates increment or adjust elements one by one, then hit later indices that break their logic. The trick is realizing prefix operations affect everything downstream, so you need to track cumulative change or work differently.
How does prefix sum connect to the solution?+
Prefix sums let you compute cumulative effect of range operations in O(1) after O(n) preprocessing. Instead of actually updating subarrays, you track the net change applied up to each index, which answers 'what adjustments have been made to this element so far'.
Is this problem suitable for a 30-minute OA block?+
If you know the pattern, yes. If you don't and have to derive it cold, it's tight. You need to recognize the prefix sum angle quickly. That's why having a safety net like StealthCoder matters for problems with this rarity.
What topics should I study before an OA with array/greedy problems?+
Master prefix sums, cumulative difference arrays, and when greedy fails. Practice problems where left-to-right decisions affect future indices. The 38% acceptance rate here reflects that the intuitive approach usually doesn't work.
Want the actual problem statement? View "Make a Positive Array" on LeetCode →