Removing Stars From a String
A medium-tier problem at 78% community acceptance, tagged with String, Stack, Simulation. Reported in interviews at IBM and 1 others.
You're given a string with normal characters and asterisks. Each asterisk means delete the closest non-asterisk character to its left, then delete the asterisk itself. This problem shows up in assessments at IBM and Walmart Labs, and it's one of those deceptive mediums where the naive simulation gets messy fast. The trick is recognizing that a stack solves this in linear time without backtracking. If you hit this during your OA and the string manipulation angle throws you, StealthCoder surfaces the stack solution in seconds, invisible to the proctor.
Companies that ask "Removing Stars From a String"
Removing Stars From a String 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 StealthCoderMost candidates try to simulate the deletion process by repeatedly scanning the string or using index management, which collapses into quadratic complexity or brittle logic. The actual pattern is stack-based: iterate through each character. If it's an asterisk and the stack isn't empty, pop the last character. Otherwise, push the character. At the end, the stack contains your answer. The acceptance rate of 77.97% reflects that once you see the pattern, implementation is straightforward, but the string and simulation framing throws people off. This is classic medium difficulty: not algorithmically hard, but the wrong mental model burns you. When you blank on this live, StealthCoder eliminates the guesswork.
Pattern tags
You know the problem.
Make sure you actually pass it.
Removing Stars From a String 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. 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.
Removing Stars From a String interview FAQ
Is this really asked by major companies?+
Yes. IBM and Walmart Labs both report asking it. The 77.97% acceptance rate and medium difficulty suggest it's used as a filter question, not a gimme. It tests whether you can move past brute-force thinking into data structure intuition.
What's the trick I'm missing if my simulation is slow?+
You're likely re-scanning or re-indexing the string after each deletion. A stack eliminates that. Push characters you keep, pop on asterisk. One pass, O(n) time, O(n) space. The string and simulation topics are red herrings; the stack is the real insight.
How do I know when to use a stack vs. other approaches?+
Stack shines when you need to 'undo' or match pairs in one pass. Here, asterisks undo the previous character. If your approach involves revisiting old characters or index juggling, think stack. That pattern applies across string problems, not just this one.
Will I get partial credit if my solution times out?+
Most online assessments grade all-or-nothing on test cases. A quadratic simulation will fail large inputs silently. Stack-based solutions are fast enough to pass everything, so the difference between a brute-force attempt and the real solution is often AC vs. TLE, not partial points.
What if I see this in my OA cold?+
Read the problem twice. Identify that asterisks delete backwards. Recognize you're 'undoing' characters. That cue triggers stack. If you blank or panic on the pattern, StealthCoder runs invisibly during screen share and hands you the working code in seconds.
Want the actual problem statement? View "Removing Stars From a String" on LeetCode →