Anthropic phone screen experience

Just had my Anthropic phone screen this week, on the CodeSignal setup that actually opens as a notebook, no autocomplete which threw me off immediately.

Got a coding question I hadn't seen written up anywhere before. You're given an instructions file that's basically a tiny made up language for a bootloader. Each line is one of three ops, something like plus, next, and jump. Plus adds a value to a running accumulator, next just moves you down to the following line, and jump moves execution by a relative offset instead of going in order. So you start walking through the file line by line executing whatever op sits there, until you either run off the end of the file or get stuck looping.

The actual ask was to detect when execution is stuck in an infinite loop, meaning you've re-hit the same line more than once, and then figure out which line is causing it. Turned out the bug was that on one specific line, the jump and next got swapped from what they should have been, and fixing it just meant swapping them back so execution could finally escape. Then you had to return whatever the accumulator held right before it entered the loop, not whatever it piles up from looping forever.

Took me a good ten minutes just to wrap my head around what the ops were actually doing. Implementation itself honestly wasn't bad once that clicked. Ran out of time before I could really dig into the follow up they hinted at.

No idea if I passed yet, will update when I hear back.