Calculate Score After Performing Instructions
A medium-tier problem at 56% community acceptance, tagged with Array, Hash Table, String. Reported in interviews at Apple and 0 others.
Apple has asked this one, and it's exactly the kind of simulation problem that looks simple until you code it wrong under pressure. You're given a starting position and a string of instructions (U, D, L, R) that move a point around, plus obstacles to avoid. The trap is that most candidates write it correctly but inefficiently, or miss the obstacle logic entirely. It's a medium difficulty problem with about 55% acceptance, which means half the people who attempt it fail. This is the exact moment StealthCoder pays for itself: if you blank on how to handle the movement loop or obstacle checking during your live OA, it surfaces a working solution invisibly while you keep typing.
Companies that ask "Calculate Score After Performing Instructions"
Calculate Score After Performing Instructions 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 Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE.
Get StealthCoderThe core pattern is straightforward simulation: maintain x and y coordinates, iterate through each instruction character, update position, check if the new position hits an obstacle (usually stored in a set or hash table for O(1) lookup), and only move if clear. The mistake most candidates make is either forgetting to check obstacles before moving, or storing obstacles inefficiently and tanking performance on large inputs. String parsing is trivial, but the logic around state management and collision detection is where the false starts happen. If you've drilled this exact pattern before, you'll write it in 90 seconds. If you haven't, or if the obstacle data structure isn't immediately obvious under time pressure, that's where StealthCoder's invisible real-time solution becomes your safety net during the actual assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Calculate Score After Performing Instructions 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 Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Calculate Score After Performing Instructions interview FAQ
Is this problem really asked at Apple, and how often?+
Yes, Apple has reported this problem. It appears in their interview reports, though it's not a top-tier frequency ask. Medium difficulty sim problems show up across tech firms regularly, so if you see it on your OA, expect it's live.
What's the trick I'm missing that makes this a 55% failure rate?+
Most failures come from skipping obstacle validation before updating position, or iterating the obstacle set naively instead of storing it in a hash table. Candidates also sometimes parse the instruction string wrong or forget to initialize coordinates. Simulation problems punish small logic errors heavily.
Do I need a fancy data structure for obstacles?+
No. A set or hash table with (x, y) tuples as keys is sufficient and fast enough. You iterate instructions once (O(n)) and check each new position in O(1). That's optimal. Over-engineering here wastes time.
How does this relate to other simulation and string problems I should know?+
This combines Array/Hash Table indexing with String character iteration and collision detection. It's a template for any 'follow instructions and track state' problem. Master this pattern and you'll recognize it in grid-walk, robot, and path-tracking OAs.
If I blank on this during my OA, what's the fastest recovery?+
Pseudo-code the state update loop and obstacle check first, don't jump to syntax. Trace through a simple example by hand. If you're still stuck after 3-4 minutes, that's when StealthCoder runs invisibly and gives you the working code so you move on and don't lose the whole OA.
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