Maximum Number of Vowels in a Substring of Given Length
A medium-tier problem at 60% community acceptance, tagged with String, Sliding Window. Reported in interviews at Wayfair and 1 others.
Maximum Number of Vowels in a Substring of Given Length is a medium-difficulty string problem that shows up at Wayfair and Turing. The premise is simple: find the most vowels packed into any window of fixed size within a string. Sounds trivial until you code the naive approach and realize you're iterating the same substring repeatedly. With a 60% acceptance rate, most people know sliding window exists but mess up the implementation or miss that this is the exact use case for that pattern. If this hits your live assessment and you blank on optimization, StealthCoder surfaces a working solution invisible to the proctor.
Companies that ask "Maximum Number of Vowels in a Substring of Given Length"
Maximum Number of Vowels in a Substring of Given Length 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 by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know.
Get StealthCoderThe trap is counting vowels in every possible substring of length k by brute force, which costs O(n*k) and feels slow. The pattern is a fixed-size sliding window: build your first window, count vowels, then slide right one character at a time, subtracting the left character if it's a vowel and adding the new right character if it's a vowel. This drops you to O(n) with one pass. The trick is resisting the urge to recount the entire window each iteration. Most errors come from off-by-one bounds on the window or forgetting to check if a character is actually a vowel before subtracting. StealthCoder is the safety net if you freeze on the optimization step during live test.
Pattern tags
You know the problem.
Make sure you actually pass it.
Maximum Number of Vowels in a Substring of Given Length 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. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Maximum Number of Vowels in a Substring of Given Length interview FAQ
Is this really a medium problem, or does it feel easier in practice?+
The 60% acceptance rate reflects that the concept is straightforward but implementation speed matters. If you instantly recognize sliding window, it's a one-pass solve. If not, you'll hit time limits or write clunky code. Medium is fair.
Does Wayfair or Turing ask this in their main loop, or is it a screening question?+
We only know these two companies have asked it in reports. No data on which stage of the funnel it appears. Treat it as a full-loop candidate and code it clean.
What's the exact trick I'm missing if I code it slow?+
Not using sliding window and instead recounting vowels in each substring of length k. Build window once, then move the boundary one step at a time, add/subtract single characters. That's O(n) instead of O(n*k).
Does the language I use matter for this problem?+
No. This is pure string iteration and counting. Works the same in Python, Java, JavaScript, or C++. Pick what you're fastest in. The bottleneck is algorithm, not syntax.
How does this relate to other sliding window problems I should know?+
This is the simplest sliding window: fixed size, stateless counter. Once you own this, you can move to variable-size windows like longest substring without repeating chars. Start here, then scale.
Want the actual problem statement? View "Maximum Number of Vowels in a Substring of Given Length" on LeetCode →