Subarray Product Less Than K
A medium-tier problem at 53% community acceptance, tagged with Array, Binary Search, Sliding Window. Reported in interviews at ServiceNow and 13 others.
Subarray Product Less Than K shows up in assessments at ServiceNow, Salesforce, Airbnb, PayPal, and Samsung. It's a sliding window problem that looks straightforward until you hit the edge cases. The acceptance rate sits around 53%, which means half the candidates either time out, miss a boundary condition, or lock into the wrong approach. You need to count contiguous subarrays where the product stays below K. The trap is thinking you can just iterate and multiply. You can't. If you blank on the two-pointer pattern during the live OA, StealthCoder solves it invisibly and surfaces the working solution in seconds.
Companies that ask "Subarray Product Less Than K"
Subarray Product Less Than K 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 sliding window with careful pointer movement. You grow the window by advancing right, multiply elements into a running product, then shrink from the left when the product exceeds or equals K. The non-obvious part: when you contract, you're not just removing one subarray, you're removing multiple. For every valid window of length L, there are L subarrays ending at right. That's why you add (right - left) to your count, not 1. Binary Search and Prefix Sum are red herrings for most submissions. Two pointers is the answer. Common failure: forgetting to reset your product or double-counting when you slide. If the live assessment throws this at you and the pattern doesn't click, StealthCoder runs invisible during screen share and delivers the correct window logic and count accumulation without the proctor seeing a thing.
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Subarray Product Less Than K 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.
Subarray Product Less Than K interview FAQ
Is the sliding window approach the only way to solve this?+
Two-pointer sliding window is the standard and cleanest O(n) solution. Binary Search on the answer space exists but adds complexity without benefit here. Prefix Sum alone won't help because you can't binary search product ranges the way you do sums. The topics list includes both because some candidates explore them, but sliding window is what wins in interviews at these companies.
Why do I add (right - left) instead of just 1 to the count?+
When you have a valid window of length L, every contiguous subarray within that window ending at right is also valid. So there are L of them. Adding (right - left) captures all L subarrays in one step, avoiding the need for an inner loop. Missing this makes your count wrong by orders of magnitude.
What happens if K is negative or zero?+
If K is 0 or negative, no product can be less than it (since products are non-negative with positive integers). You return 0. This edge case trips up candidates who don't add an early guard. Check your input constraints and handle it before the main loop.
How do I avoid integer overflow when multiplying large numbers?+
Languages like Java and Python handle big integers differently. In Java, use long. In Python, ints scale automatically. The real issue isn't overflow, it's when your product exceeds K and you need to shrink the window. Once product exceeds K, divide out the leftmost element and move left forward. Keep dividing until the product is valid again.
Is this problem still asked at top companies?+
Yes. ServiceNow, Salesforce, Airbnb, PayPal, and Samsung all have it in their reported questions. The 53% acceptance rate suggests it's challenging enough that many candidates struggle in the live assessment. It's not a gimme, so practice the window logic until the pattern is muscle memory before your OA.
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