Odd String Difference
A easy-tier problem at 61% community acceptance, tagged with Array, Hash Table, String. Reported in interviews at Visa and 2 others.
Odd String Difference is a deceptively simple problem that shows up in online assessments at Visa, Datadog, and IBM. With a 61% acceptance rate, it's not a gimme, which means plenty of candidates overcomplicate it or miss the pattern entirely. The trick isn't in the algorithm, it's in seeing what the problem is actually asking. If you blank on it during the live OA, StealthCoder reads the problem and surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Odd String Difference"
Odd String Difference 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 for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe problem plays on string encoding and hash tables to identify an outlier. Most candidates start building complex difference matrices or multi-pass loops when the optimal approach uses a single pass and a simple collision detector. The pattern: one string's encoding is different from all the others, and you need to spot it fast. Where people falter: they think they need to store all differences, or they second-guess whether a hash table is necessary. The actual solution is elegant once you see it, but that moment of clarity doesn't always hit under pressure. This is exactly the scenario where StealthCoder becomes your safety net, especially if the problem statement is ambiguous or you misread which string is the outlier.
Pattern tags
You know the problem.
Make sure you actually pass it.
Odd String Difference 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 for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Odd String Difference interview FAQ
Is this really just an easy problem or does it have a trick?+
It's genuinely easy once you see the pattern, but the acceptance rate at 61% suggests many candidates overthink it or misread the problem. The trick is recognizing that a hash table collision or XOR check will expose the odd one out. Speed comes from not building unnecessary data structures.
Do I need to implement a complex difference-matching algorithm?+
No. The problem rewards clean, direct logic. Most solutions use hash tables or bitwise operations to identify the outlier in a single pass. If you're writing nested loops or storing intermediate results across multiple passes, you're overcomplicating it.
How does this relate to the Array and String topics?+
You're iterating through strings (String topic) and comparing them efficiently, often using a data structure to track differences (Array, Hash Table topics). The problem tests whether you can combine these concepts without waste.
Is this still asked at these companies?+
Yes, Visa, Datadog, and IBM have reported asking it. It's a quick filter question, not a deep-dive interview problem. It separates candidates who code carefully from those who code carelessly under pressure.
What's the most common wrong approach?+
Comparing every string against every other string in nested loops, then trying to reason about the results. The right move is to encode each string's character differences into a hash or signature, then find the one that appears once.
Want the actual problem statement? View "Odd String Difference" on LeetCode →