Repeated Substring Pattern
A easy-tier problem at 47% community acceptance, tagged with String, String Matching. Reported in interviews at Myntra and 1 others.
Repeated Substring Pattern is an easy string problem that looks deceptively simple until you hit the trick during a live assessment. You're given a string and need to determine if it's made up entirely of a repeating substring. The naive approach of checking all divisors of the string length will work, but it's slow and makes you look like you don't know the pattern. Myntra and Salesforce have both asked this. The acceptance rate sits at 46%, which means nearly half the candidates either time out or miss the clever string-matching insight entirely. If you blank on the shortcut during your OA, StealthCoder solves it invisibly in seconds.
Companies that ask "Repeated Substring Pattern"
Repeated Substring Pattern 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 StealthCoderThe trick is understanding that if a string is a repeated pattern, you can detect it without iteration through divisors. The classic insight: if string S is made of a repeating substring, then S will always appear in (S+S) at a position other than 0 or len(S). This uses String Matching principles to solve what looks like a divisor-checking problem. The brute-force path is checking every divisor of the string length and validating each one, which works but screams inefficiency in an interview. The pattern-based approach is instant and elegant. Most candidates either grind through divisor loops or try regex without understanding the mathematical principle. When you hit this live and the obvious loop doesn't feel right, StealthCoder gives you the concatenation trick instantly, letting you move on.
Pattern tags
You know the problem.
Make sure you actually pass it.
Repeated Substring Pattern 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 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.
Repeated Substring Pattern interview FAQ
Is this really an easy problem or is the acceptance rate misleading?+
The 46% acceptance rate suggests the trick isn't obvious under interview pressure. The problem is classified easy because once you know the pattern, it's a one-liner. But candidates who don't know the concatenation trick waste time on divisor loops or submit slow solutions. Know the pattern, it's trivial. Miss it, it's a trap.
What's the actual algorithmic trick?+
If a string S is built from a repeating substring, then S will appear inside (S+S) at some position between 1 and len(S)-1. This leverages string matching to avoid explicit divisor checking. It's based on the mathematical property that repeating patterns create this overlap property.
Do I need to check every divisor of the string length?+
That approach works but it's inefficient and signals you don't know the pattern. The concatenation method is constant time relative to string matching, and it's the insight interviewers expect at companies like Myntra and Salesforce. Divisor checking is the brute-force backup if you're stuck.
Why do Myntra and Salesforce ask this if it's easy?+
Easy problems filter for whether you know common patterns or whether you'll waste time grinding loops. It's a speed check. Both companies value engineers who recognize tricks without overthinking. It's not about difficulty, it's about pattern recognition and confidence under pressure.
What string matching concepts does this rely on?+
The problem uses the idea that repeating substrings create predictable patterns when concatenated. If you understand KMP or basic string overlap, the insight clicks immediately. This is why it's classified under String Matching topics, not just String manipulation.
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