Day 20: Grove Positioning System
Nim: Part 1 (02:57:50, rank 3876), Part 2 (03:01:14, rank 3357)
Modulo logic...
This one was really confusing for me. I wasn't sure exactly what should happen in the edge cases like [-1,0,0,0] or [0,0,0,5] etc. I ended up with some really confusing conditions. Eventually I started echoing in some simple examples and reduced the logic to "determine target position, then the number of left/right swaps to get there".
The extension to part 2 was very trivial this time -- part 1 was really the hard part.
(none)
Too early in the morning for thinking about modulo and wrapping around a queue... But as is often the case, I should have started making a set of simple testcases sooner, since even "obvious" cases like 0 0 0 1 and -2 0 0 0 revealed that I'd misunderstood the spec. Working through some examples with 4 numbers, it quickly became apparent that numbers will either stay in place or shift to one of 3 other positions, indicating that for N numbers, a modulo (N-1) step will be required.