Find Last Characters
Reported by candidates from Google's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Google's "Find Last Characters" question hit the assessment circuit in June 2024, and it's deceptively simple on the surface. You're looking at a string manipulation problem that feels like it should be a one-liner but has a real edge case underneath. Most candidates blank on the boundary condition or overthink the traversal. StealthCoder sits in the corner and catches the pattern the moment you read it, so you're not stuck guessing how to walk backwards through a string or handle an empty result.
Pattern and pitfall
The core trick here is understanding what "last characters" really means in context. You're likely iterating from the end of a string or array backward, either to extract a suffix, find the last occurrence of something, or reconstruct in reverse order. The pitfall: off-by-one errors when indexing, or assuming the input is never empty or malformed. The algorithm is usually O(n) linear scan, sometimes with a hash table if you need to track frequency of those last characters. StealthCoder will show you the exact boundary checks and loop termination logic the moment you see the problem statement, which is your safety net if you freeze up during the live OA.
Drill it cold or hedge it with StealthCoder. Either way, don't walk into the OA hoping you remember the trick.
You can drill Find Last Characters 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. Made for the candidate who got the OA invite this morning and has 72 hours, not six months.
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Google reuses patterns across OAs. Made for the candidate who got the OA invite this morning and has 72 hours, not six months. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Find Last Characters FAQ
Is this a string manipulation problem or something deeper?+
It's string manipulation with a twist. You're not just slicing or reversing. The question is testing whether you handle edge cases: what if the string is shorter than the number of characters you need? What if it's empty? How do you avoid index out of bounds?
How do I prepare for this in 24 hours?+
Understand Python string slicing or your language's substring methods cold. Practice iterating backwards through arrays using negative indexing or a manual loop with a pointer. Run through examples with empty strings, single characters, and strings shorter than your target length.
Will this show up exactly the same in my OA?+
The core idea stays the same: extract or identify the last N characters or the final occurrence of a pattern. The wording or context might change, but the algorithm and pitfalls remain. Know how to code it without thinking.
Is there a trick or a gotcha I should know about?+
Yes. Google loves boundary tests. They'll either give you a string shorter than your target, or a degenerate input like an empty string or single character. Make sure your code doesn't crash. That's often the difference between pass and fail.
What if I freeze during the OA?+
You have a live fallback. Read the problem aloud. Write pseudocode first: loop backward, handle the edge case, return the result. StealthCoder will fill the gaps if you blank on syntax, so you stay in the game.