Min Operations
Reported by candidates from Amazon's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
You've got an Amazon OA in your inbox and "Min Operations" is on it. December 2024 data shows this problem tests whether you can work backwards from a goal state, or spot a greedy pattern that cuts through what looks like a search problem. You're probably staring at some transformation rule and counting steps. The trick is almost always to reverse the operation or find the mathematical shortcut instead of simulating forward. StealthCoder sits quietly in the background during your live OA, ready to feed you the approach if you freeze on implementation.
Pattern and pitfall
Min Operations typically gives you a starting value (usually 1) and a target, with one or two allowed moves per step. Most candidates simulate forward, building a BFS or trying DFS, which works but eats time. The real pattern is to reverse: start at the target, undo operations, and count steps back to 1. This collapses exponential search space into linear or logarithmic time. If the operations are arithmetic (multiply by 2, add 1, divide by 3), reversing often reveals a greedy choice at each step. Amazon likes this problem because it separates pattern-spotters from brute-forcers. When you're live and your first approach feels slow, StealthCoder can confirm whether reversal is the move.
Drill it cold or hedge it with StealthCoder. Either way, don't walk into the OA hoping you remember the trick.
You can drill Min Operations 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. Made for the candidate who got the OA invite this morning and has 72 hours, not six months.
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Amazon reuses patterns across OAs. Made for the candidate who got the OA invite this morning and has 72 hours, not six months. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Min Operations FAQ
Is this a BFS problem or can I solve it mathematically?+
Mathematical. Most "min operations" problems on Amazon collapse when you reverse the operations and work backwards from target to 1. Greedy choices become obvious in reverse. BFS works but it's slower and signals you missed the insight.
What's the most common pitfall?+
Simulating forward with DFS or naive BFS instead of reversing. Forward search often hits timeout on large targets. Always test reversal first. It's counterintuitive but it's the pattern Amazon wants to see.
How do I know which operation to undo first when there are multiple choices?+
If reversal is the right approach, often one operation dominates (e.g., dividing by 2 reduces faster than subtracting 1). Greedy choice in reverse is usually the optimal choice. Try the operation that shrinks the number fastest.
Should I code both forward and reverse as a safety net?+
No. Pick one, test it on the examples, and commit. Reverse almost always wins on Amazon min-operation problems. Coding both wastes time and signals doubt. Know the pattern before you start typing.
What if reversal doesn't work cleanly?+
The operations might require BFS or dynamic programming. But Amazon's "min operations" is almost always reversal. If your reversal solution doesn't pass examples, re-read the operations. You likely misunderstood the rule.