Clear Digits
A easy-tier problem at 83% community acceptance, tagged with String, Stack, Simulation. Reported in interviews at Flexera and 0 others.
Clear Digits is an easy problem that shows up in Flexera interviews and passes at an 82% acceptance rate. It's deceptively simple on the surface, which means most candidates don't prepare for it, then blank when it appears on a live assessment. The twist isn't in the algorithm, it's that you need to recognize the exact moment to apply the right data structure. If this problem hits your online assessment and you freeze on how to track state, StealthCoder solves it in seconds invisible to the proctor.
Companies that ask "Clear Digits"
Clear Digits 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. Made by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too.
Get StealthCoderThe problem asks you to simulate removing digit-letter pairs from a string. The naive approach, iterate through and delete as you go, will break your indexing. The actual pattern is stack-based: push characters onto a stack, and when you see a digit, pop the previous character (guaranteed to be a letter). This turns linear manipulation into constant-time pair removal. Most candidates either over-engineer with regex or get caught in index-tracking bugs. The simulation topic is here because you're modeling a state machine, but the real execution relies on recognizing that a stack matches the LIFO behavior of 'clear the last letter before this digit'. If this specific pattern hasn't clicked in your drills, StealthCoder is the hedge that surfaces a working solution during the live OA.
Pattern tags
You know the problem.
Make sure you actually pass it.
Clear Digits recycles across companies for a reason. It's easy-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. Made by an Amazon engineer who watched the leaked-problem repo become an industry secret. He decided you should have it too. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Clear Digits interview FAQ
Is Clear Digits actually easy or does the acceptance rate lie?+
The 82% acceptance rate is honest. It's easy if you see the stack pattern. Most fails come from candidates trying to manipulate the string in-place or overthinking state tracking. Once you recognize it as a stack problem, the solution is five lines of clean code.
Will Flexera ask this as a follow-up or standalone?+
Based on the data, it shows up in their assessments. They likely use it as a quick warm-up or filter question, not as a complex multi-part interview. Treat it as a speed question: you should solve it under two minutes once you've seen the stack pattern.
What's the trick I'm missing if I keep timing out?+
You're probably mutating the string instead of using a stack. String removal in a loop causes O(n^2) behavior because each deletion shifts indices. Stack push-pop is O(n) single pass. Switch to stack, your runtime collapses.
Is this really just String and Stack or is there a Simulation angle I'm missing?+
It's all three. You're simulating a process (clearing pairs), using a stack to implement it efficiently, and the output is a modified string. The topics overlap intentionally. Focus on the stack; the others follow.
Should I memorize this pattern or understand it?+
Understand it. This stack-on-digit-pop-previous pattern shows up in parentheses matching, asteroid collision, and more. If you drill the principle once, you'll spot it across multiple problems. One pattern, many problems.
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