Lexicographically Maximal Resulting Array
Reported by candidates from Amazon's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Amazon's May 2025 OA includes a lexicographically maximal array problem. You're given an array and some operation (swap, remove, rearrange, or transform elements), and you need to return the state that's lexicographically largest. The trap is that greedy doesn't always work straight through from left to right. You need to see when to backtrack or when a later move unlocks a better overall result. StealthCoder reads the exact operation rules and surfaces the right pattern in seconds if you blank.
Pattern and pitfall
The core trick here is greedy placement with lookahead. Most candidates code a naive left-to-right greedy pass and get partial credit. The real solution often requires you to build the result by always placing the maximum available element at the current position, but 'available' depends on what operations are legal and what indices you can still reach. Some versions need a monotonic stack or a sliding window to track feasible swaps. The pattern is array manipulation with greedy construction, sometimes mixed with sorting or priority queues. If the operation is 'swap adjacent pairs up to K times,' you're looking at a permutation search space. If it's 'remove elements to maximize remaining,' it's a filtering problem. StealthCoder will extract the constraint and show you the exact greedy order or dynamic-programming fallback before you second-guess yourself.
If you see this problem in your OA tomorrow, the play is to recognize the pattern in 30 seconds. StealthCoder buys you that recognition.
You can drill Lexicographically Maximal Resulting Array cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken.
Get StealthCoderRelated leaked OAs
You've seen the question.
Make sure you actually pass Amazon's OA.
Amazon reuses patterns across OAs. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Lexicographically Maximal Resulting Array FAQ
Is this just a greedy left-to-right pass?+
Not always. Greedy works for the first position, but you may need to backtrack or defer a choice to unlock a better position later. The 'lexicographically maximal' anchor is position 0, but the operation rules determine if you can always swap or move elements freely. Read the constraints carefully.
What's the difference between this and sorting?+
If you can sort freely, it's trivial (reverse sort). This problem restricts operations: maybe you can only swap adjacent elements, or swap within a window, or remove some. The constraint is the problem. Identify it immediately.
Do I need dynamic programming here?+
Unlikely, unless the operation count is limited and you need to explore decision trees. Most 'lexicographically maximal array' problems solve in O(n^2) or O(n log n) with greedy or a single pass through a priority queue. DP is the backup if greedy doesn't nail it.
How do I test if my greedy is correct before submitting?+
Walk through a small example (n=4 or 5) by hand. For each position from left to right, ask: what's the largest element I can legally place here without violating future constraints? If your greedy answer matches your manual trace, you're likely safe.
What if I don't understand the operation in the first 30 seconds?+
Read the operation definition three times and find one concrete example. Restate it aloud: 'I can swap indices i and j if...'. Once the boundary is clear, the greedy strategy usually falls out. If it doesn't, it's a simulation or search problem, not a trick.