Get Num Perfect Packing
Reported by candidates from Amazon's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Amazon's Get Num Perfect Packing question hit the OA circuit in November 2024, and it's a deceptive math problem wrapped in a packing metaphor. You're given some form of input about items or containers, and the goal is to find the count of 'perfect' arrangements or configurations. The trick isn't brute force. It's recognizing the mathematical property that makes a packing 'perfect' and then counting configurations that satisfy it. StealthCoder will catch the pattern if you blank on the modular arithmetic or combinatorial formula mid-assessment.
Pattern and pitfall
The problem likely hinges on a specific mathematical constraint: divisibility, balance, or pairing that defines 'perfect'. You won't iterate through all possibilities. Instead, you'll derive a formula or recognize a counting pattern. Common pitfalls: assuming brute force works within time limits, missing that the constraint is about equal distribution or modular equivalence, and not pre-computing results for large inputs. The real work is identifying what makes a packing 'perfect' from the problem statement, then translating that into a counting or validation function. If you're stuck on the logic, StealthCoder reading the exact wording in real time is your safety net to decode the constraint and spot the formula.
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 Get Num Perfect Packing 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.
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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.
Get Num Perfect Packing FAQ
Is this a combinatorics or a simulation problem?+
Combinatorics, almost certainly. You're counting configurations that meet a criteria, not building them step by step. Look for a math formula or a closed-form pattern rather than nested loops.
What does 'perfect packing' actually mean in the problem?+
That depends on the exact wording you see on test day. It likely means items or values fit into bins or pairs such that some property holds. divisibility by a number, equal sums, or symmetric arrangement are common flavors. Read the problem statement carefully.
Should I precompute anything?+
Yes, probably. If the input is a number or a list up to a certain size, precompute the count of perfect packings for all smaller values using dynamic programming or a mathematical formula.
How hard is this compared to typical Amazon OA problems?+
Medium to hard. It's not a graph or tree problem, which makes it less familiar. The difficulty is in recognizing the pattern, not the implementation once you see it.
Can I solve this in 48 hours of prep?+
If you focus on math-based counting problems and understand modular arithmetic or combinatorics basics, yes. Drill LeetCode problems tagged 'math' and 'counting'. The insight matters more than grinding code.