Remove K Digits
A medium-tier problem at 35% community acceptance, tagged with String, Stack, Greedy. Reported in interviews at Snap and 9 others.
Remove K Digits is a medium-difficulty string problem that shows up across tech interviews at Snap, Snowflake, DE Shaw, Samsung, and others. The acceptance rate sits around 35%, which means most candidates who see it live either miss the greedy pattern or build a solution that times out. The trick isn't obvious from the problem statement, and if you blank on it during your assessment, you won't have time to reverse-engineer the approach. StealthCoder is the safety net for this one: if it appears in your OA and the pattern doesn't click, it surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Remove K Digits"
Remove K 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. Built by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code.
Get StealthCoderThe problem feels like a string manipulation task, but the optimal path uses a monotonic stack with greedy logic. Most candidates try to iterate through and remove digits naively, which works but misses the key insight: you want to remove larger digits early so smaller ones move to the front. A stack-based approach where you pop larger elements when a smaller digit arrives, then trim the remaining stack, solves it in linear time. The pitfall is off-by-one errors on the trim, or not recognizing that this is a greedy + stack combo, not a pure string problem. Common implementations in your OA timeout because they don't use the stack pattern. Understanding when monotonic stack applies (whenever you're hunting for the next smaller or larger element with constraints) is the bridge between this problem and others tagged Stack and Greedy.
Pattern tags
You know the problem.
Make sure you actually pass it.
Remove K Digits 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 by an Amazon engineer who realized the OA tests how well you memorized 200 problems, not how well you code. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Remove K Digits interview FAQ
Is this still asked at Snap, Snowflake, and these other companies?+
Yes. Ten companies across the input list have asked it, including Snap, Snowflake, DE Shaw, and Samsung. It appears frequently enough in reports that you should have a solution drilled. The 35% acceptance rate means it's not a gimme, but it's not an outlier either.
What's the actual trick most people miss?+
The greedy monotonic stack approach. Candidates try string slicing or deletion loops and hit timeout. The pattern is: iterate through digits, pop from stack when the current digit is smaller than the stack top (and removals remain), then push the current digit. Trim excess from the end if removals are left.
How does this relate to the Monotonic Stack topic?+
Monotonic stack is the core technique here. You maintain a stack where elements are in increasing order, popping when a smaller element arrives. This pattern shows up in 'next greater element' and similar problems. Mastering it on this problem transfers directly to others tagged Monotonic Stack.
What are the common edge cases that cause WA or runtime errors?+
Leading zeros in the result (process them after stack work), empty string result (return '0'), and off-by-one when trimming the stack if removals remain. The second loop to trim is easy to get wrong. Test cases with all the same digit and with K larger than the string length catch these.
If I hit this live and blank on the stack pattern, what's my fallback?+
StealthCoder solves it in seconds, invisible during screen share. You get a working solution you can submit and move on. The live OA isn't the place to reverse-engineer a greedy pattern under pressure.
Want the actual problem statement? View "Remove K Digits" on LeetCode →