Pass the Pillow
A easy-tier problem at 57% community acceptance, tagged with Math, Simulation. Reported in interviews at MathWorks and 0 others.
Pass the Pillow is a math simulation problem that sounds deceptively simple but trips up candidates who don't map the pattern clearly. MathWorks has asked it. The acceptance rate sits at 57%, which means half the people who see it either overthink the simulation or miss the mathematical trick that collapses the problem into a closed-form answer. You don't need a complex loop or state machine. The pillow follows a predictable bouncing pattern, and once you see it, the answer is a one-liner. If this shows up in your live OA and you blank on the cycle, StealthCoder solves it in seconds invisible to the proctor.
Companies that ask "Pass the Pillow"
Pass the Pillow 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 for the engineer who has done the work but might still blank with a webcam pointed at him.
Get StealthCoderThe trap is treating this as a full simulation when it's really a math problem. Candidates start building loops to track position and direction, updating state each round. That works but misses the elegant pattern: the pillow bounces back and forth in a cycle of predictable length. The math insight is recognizing the period and using modular arithmetic to jump straight to the answer without iterating through every step. The simulation approach isn't wrong, just inefficient and prone to off-by-one errors. Most failures come from direction-flip logic or miscounting rounds. The real skill here is pattern recognition, not coding. Once you see the cycle length and remainder, you're done. If you haven't drilled this exact pattern before and hit it live, StealthCoder surfaces the closed-form solution immediately, sidestepping the brute-force trap.
Pattern tags
You know the problem.
Make sure you actually pass it.
Pass the Pillow 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. Made for the engineer who has done the work but might still blank with a webcam pointed at him. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Pass the Pillow interview FAQ
Is Pass the Pillow really just a simulation problem?+
No. While you can solve it with a loop, the intended approach is mathematical. The pillow follows a repeating cycle, and the answer is modular arithmetic applied to that cycle. Simulation works but signals you missed the pattern, which interviewers notice.
What's the main trick to Pass the Pillow?+
Find the cycle length. The pillow bounces back and forth in a fixed pattern. Use modulo to find where in the cycle you land after n rounds. No loops needed. Most candidates waste time iterating when one formula gives the answer.
Why is the acceptance rate only 57% on an Easy problem?+
Direction-flip logic and off-by-one errors kill simulation approaches. People also underestimate the problem and code sloppily. The math insight isn't obvious if you don't pattern-match to modular arithmetic problems you've seen before.
Does MathWorks ask this in real interviews?+
Yes, it's in their reported assessment mix. MathWorks hires for roles that value mathematical thinking, so a problem that rewards pattern recognition over brute force fits their bar. Expect similar problems in that pipeline.
How do I avoid the simulation trap?+
Read the problem, then ask yourself: what repeats? Don't code until you've drawn out a few rounds and identified the cycle. Once you have the cycle length, math solves it. Writing code first is how people fail this one.
Want the actual problem statement? View "Pass the Pillow" on LeetCode →