Max Difference You Can Get From Changing an Integer
A medium-tier problem at 49% community acceptance, tagged with Math, Greedy. Reported in interviews at Trexquant and 1 others.
You're staring at a problem that sounds simple until you realize the greedy choices matter. Max Difference You Can Get From Changing an Integer sits at medium difficulty with a 49% acceptance rate, which means half the candidates who see it either miss the trick or implement it sloppily. It's been asked at Trexquant and Mercari. The core idea: you can replace digit characters in a number string to maximize the difference between a large version and a small version of the same number. This is pure greedy logic, but the execution has teeth. If you hit this during a live assessment and blank on the digit-swapping rules, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Max Difference You Can Get From Changing an Integer"
Max Difference You Can Get From Changing an Integer 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 trap is thinking this is about brute force or dynamic programming. It's not. You need to understand that maximizing difference means making one number as large as possible and another as small as possible by strategically replacing digit characters. For the maximum version, scan left to right and replace the first digit that isn't 9 with a 9. For the minimum version, handle the leading digit carefully (don't make it 0 unless it already is), then replace the first digit that isn't 0 or 1 with 0. The mistake candidates make: forgetting that you can only replace one digit character with one other digit, or getting confused about leading zeros. The problems involve Math and Greedy patterns, and both require you to commit to a replacement rule and stick with it. This is where StealthCoder bridges the gap if the greedy strategy doesn't click during your timed assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Max Difference You Can Get From Changing an Integer 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.
Max Difference You Can Get From Changing an Integer interview FAQ
Is this problem actually medium difficulty?+
The 49% acceptance rate suggests the difficulty label is fair. Many candidates understand the concept but botch the implementation details around leading zeros or digit replacement logic. The greedy strategy itself is straightforward once you see it, but the rules are strict.
What's the trick I'm missing if I get wrong answer?+
Three common mistakes: treating max and min the same way (you can't just flip all digits), forgetting that the leading digit of minimum can't become 0 unless it already is, or replacing the wrong first occurrence of a digit. Think 'replace only one digit character with one other digit'.
How does this relate to Greedy?+
Greedy means you make the locally optimal choice at each step without backtracking. Here, scan left to right and commit to replacing the first digit that satisfies your rule. For max, replace the first non-9. For min, replace the first non-0 (and not the leading digit if it would create a zero).
Will I see this at Trexquant or Mercari?+
Both companies have reported asking it. If you're interviewing there, this is a real possibility. It's the kind of problem that fits well with quantitative firms and mid-size tech shops because it tests whether you can reason about digit manipulation under constraints.
How long should this take in a real assessment?+
If you see the greedy pattern, 10 to 15 minutes to code and test. If you don't, you can spin your wheels. That's why the 49% acceptance rate is real. Have the strategy locked in before you start typing, or have a backup plan if you get stuck.
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