Steps to Make Array Non-decreasing
A medium-tier problem at 23% community acceptance, tagged with Array, Linked List, Stack. Reported in interviews at Morgan Stanley and 0 others.
You're staring at an array that needs to become non-decreasing, and the brute-force approach of checking every possible removal blows up in O(n^2) or worse. This problem hits the MEDIUM difficulty but sits in the bottom quartile of acceptance rates at 23 percent, which means most candidates either miss the monotonic stack pattern or get tangled in edge cases. Morgan Stanley has asked it. The trick isn't obvious until you realize you're not just removing elements randomly, you're building a valid sequence by deciding which element to sacrifice when a decrease happens. If this problem lands in your OA and you freeze on the pattern, StealthCoder runs invisibly during your screen share and surfaces a working solution in seconds.
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Steps to Make Array Non-decreasing 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 engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoderThe core insight is that you iterate through the array and maintain a monotonic stack of elements in non-decreasing order. When you encounter a value smaller than the stack top, you pop elements from the stack until the stack is empty or you find an element smaller than or equal to the current value. The catch is deciding which elements to remove counts as 'steps', each pop is one step. Many candidates try a greedy approach without the stack structure and end up with sequences that aren't actually non-decreasing. The monotonic stack pattern forces you to make locally optimal decisions that compound into a globally valid solution. This also relates to how stacks handle similar problems in linked lists and array transformations. When you hit this live and the greedy intuition fails, StealthCoder gives you the exact stack-based solution so you move forward.
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Steps to Make Array Non-decreasing 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 engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Steps to Make Array Non-decreasing interview FAQ
Why is the acceptance rate so low on this problem?+
The monotonic stack pattern isn't intuitive for most candidates who default to greedy or brute-force removal. The edge cases around which element to pop and how to count steps trip up implementations. At 23 percent, this is a gatekeeping problem designed to separate candidates who've seen the pattern from those who haven't.
Is this really asked in interviews at major companies?+
Morgan Stanley has asked it. It's not as frequent as array-sorting or hash-map problems, but it appears in companies that test algorithmic depth. The low acceptance rate suggests it's used as a hard-filter question rather than a warm-up.
What's the relationship between this and the stack topic?+
The monotonic stack is the core technique. You maintain a stack where elements are in non-decreasing order, and you pop when you encounter a smaller value. Understanding monotonic stacks unlocks this problem and similar array-processing patterns where order matters.
How does linked list relate to this array problem?+
Some variants or follow-ups ask you to apply the same non-decreasing logic to linked lists instead of arrays. The core algorithm stays the same, but you're managing pointers instead of array indices. It's listed as a topic here because the problem extends naturally into linked-list territory.
What happens if I try a greedy approach without a stack?+
You'll get stuck on cases where you need to remove multiple elements in sequence. A greedy removal at each step doesn't guarantee the final array is non-decreasing. The monotonic stack forces you to backtrack and make better decisions when conflicts arise.
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