Unique Email Addresses
A easy-tier problem at 68% community acceptance, tagged with Array, Hash Table, String. Reported in interviews at Wix and 2 others.
Unique Email Addresses is a straightforward string processing problem that's popular at Wix, Intuit, and Twitch. You're given a list of email addresses and need to count how many are actually unique, accounting for Gmail's rule that dots in the local part don't matter and everything after a plus sign is ignored. It's easy on the surface, but the trick is implementing the email normalization cleanly. If you blank on the parsing logic during your assessment, StealthCoder runs invisibly and surfaces the solution in seconds, so you move on without panic.
Companies that ask "Unique Email Addresses"
Unique Email Addresses 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 forces you to understand string manipulation and hash tables together. The naive approach fails if you forget Gmail's rules or implement them sloppily. You need to parse each email, strip out dots from the part before the '@', drop everything after a plus sign (if present), then store the canonical form in a set. The common pitfall is handling the plus sign incorrectly or forgetting to normalize before hashing. Since acceptance sits around 68%, most people who see it get it right, but the parsing step is where careless candidates drop time or introduce bugs. During a live OA, if the logic isn't clicking fast, StealthCoder bridges that gap by showing a working solution, letting you code it cleanly without second-guessing the string rules.
Pattern tags
You know the problem.
Make sure you actually pass it.
Unique Email Addresses 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. 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.
Unique Email Addresses interview FAQ
Is this really an easy problem or will it trip me up in an actual interview?+
It's genuinely easy, but easy doesn't mean trivial. The acceptance rate is 68%, so most people pass. The trap is sloppy email parsing. If you test your normalization carefully (especially the plus-sign rule), you'll pass. It's not a pattern-matching problem; it's attention to detail.
What's the actual trick here? Why do Wix and Intuit ask it?+
They're testing whether you can read a spec carefully and implement string logic without bugs. There's no fancy algorithm. You parse, normalize, deduplicate with a hash table. It reveals whether you write sloppy code under pressure or think through edge cases first.
How does this relate to Hash Table and Array topics?+
You iterate over the array of email strings (Array topic), normalize each one, then use a set or hash table (Hash Table topic) to count unique values. It's a direct application: arrays hold input, hash tables solve the uniqueness problem. Both are essential.
If I see this in my OA, how much time should I spend on it?+
Five to ten minutes max if you know the Gmail rules. If you blank on the plus-sign or dot behavior, StealthCoder solves it instantly during screen share, so you don't waste time guessing. The parsing is the only real work.
Do I need to memorize the Gmail email rules for this?+
The problem statement always includes them, so no. But knowing them beforehand (dots ignored, plus signs + everything after is dropped) lets you code faster. If you don't remember during the OA, the problem description clarifies it.
Want the actual problem statement? View "Unique Email Addresses" on LeetCode →