Get Final String
Reported by candidates from JP Morgan's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
JP Morgan's 'Get Final String' problem is a string manipulation question reported in September 2024. You're working with transformations that collapse or simplify a string through repeated operations. The trick isn't brute force. It's recognizing the operation pattern and finding the efficient way to apply it until the string stabilizes. StealthCoder will catch you if you blank on the implementation during the live OA, but the real win is spotting the pattern now.
Pattern and pitfall
This is a classic iterative string reduction problem. You apply a rule (usually removing adjacent duplicates or collapsing matching pairs) until no more reductions are possible. Most candidates write a simulation loop and call it done, which often works for small inputs but times out on large ones. The pattern recognition matters: some problems hide a stack-based solution that's O(n) instead of O(n^2). Build the string by pushing characters onto a stack, checking against the top element each time. Pop if there's a match, push otherwise. Single pass, no repeated scans. If you blank on optimization during the OA, StealthCoder will show you the stack approach in real time.
If you see this problem in your OA tomorrow, the play is to recognize the pattern in 30 seconds. StealthCoder buys you that recognition.
You can drill Get Final String 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. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as remove all adjacent duplicates in string. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass JP Morgan's OA.
JP Morgan reuses patterns across OAs. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Get Final String FAQ
What's the most common pitfall on this problem?+
Writing nested loops that re-scan the string after each removal. Candidates get the right answer on small test cases, then timeout on large ones. Stack-based single pass is the intended solution. Learn it before the OA.
Is this problem about removing adjacent duplicates specifically?+
The exact rule varies, but the pattern is always: apply a removal/collapse rule repeatedly until the string stops changing. Read the problem statement carefully for the exact condition. It might be pairs, specific characters, or something else.
Do I need to handle edge cases like empty strings?+
Yes. Empty input, single character, and strings that don't change should all be tested. Edge cases are where bugs hide. If you blank during the OA, test these first after you get core logic working.
Can I solve this in Python and get away with a slower solution?+
Maybe on smaller test cases. JP Morgan's OAs typically have tight time limits. Stack solution is fast in any language. Write efficient code from the start, don't assume Python is a buffer.
How do I prepare for this in 24-48 hours if I'm rusty?+
Code the stack-based solution three times. Trace through a worked example by hand. Understand why it's O(n) not O(n^2). Skip the 'study' phase, focus on the pattern and implementation. That's it.