Shortest Uncommon Substring in an Array
A medium-tier problem at 48% community acceptance, tagged with Array, Hash Table, String. Reported in interviews at Moveworks and 2 others.
Shortest Uncommon Substring traps candidates because the obvious substring-search approach burns time and misses the pattern. It's been asked at Moveworks, Affirm, and Airbnb. The acceptance rate sits at 48%, which means nearly half the people hitting this in their OA either overthink it or code the wrong solution. The trick isn't complex, but it's easy to miss under time pressure. If you blank on the insight and your interview is live, StealthCoder surfaces the working approach invisible to the proctor.
Companies that ask "Shortest Uncommon Substring in an Array"
Shortest Uncommon Substring in an Array 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 engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share.
Get StealthCoderThis problem hinges on a single insight: you're not actually checking substrings the hard way. The 'uncommon' constraint means you're looking for something that appears in exactly one string in the array. Most candidates jump to Trie or Hash Table comparisons, which works but is overengineered. The real pattern is simpler. Once you see it, the solution shrinks from complex to trivial. The pitfall is spending 10 minutes building substring logic when the answer lives in the problem statement itself. Hash Table and Array operations are the topics listed, and they're the only tools you need. If you hit this in your OA and the brute force feels wrong, you're on the wrong path.
Pattern tags
You know the problem.
Make sure you actually pass it.
Shortest Uncommon Substring in an Array 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 engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Shortest Uncommon Substring in an Array interview FAQ
Is this actually a hard problem or does it just sound hard?+
It sounds harder than it is. The 48% acceptance rate reflects overthinking, not difficulty. Once you see the pattern, it's a one or two-liner. Most failures come from trying to build full substring-checking logic instead of reading the problem constraints carefully.
How does Trie relate to this problem?+
Trie is listed as a topic, but it's not the solution path. Trie-based approaches over-complicate it. Hash Table and Array operations are sufficient and faster. You don't need to build a tree structure here.
What's the most common mistake candidates make?+
Building substring generators and comparing them across the array. That's O(n^2) or worse and misses the actual constraint. Candidates forget to check frequency: something is 'uncommon' only if it belongs to exactly one string, not all of them.
Do companies like Airbnb and Affirm actually ask this live?+
Yes. It appears in their online assessments. The problem tests whether you can parse problem constraints under pressure. If you misread it, you code for 15 minutes on the wrong approach. That's the real test.
How much time should I spend on this if it hits my OA?+
If you see the pattern, 3 to 5 minutes. If you're still building Trie structures or nested loops after 7 minutes, step back and re-read the problem. You're on the wrong path and need to reset.
Want the actual problem statement? View "Shortest Uncommon Substring in an Array" on LeetCode →