ride VS AdventOfCode2021

Not a bad idea for current times. Dyalog APL, the only active APL compiler developer, did similar a couple of years ago with RIDE

The Linux IDE for Dyalog is Ride, packaged separately and available from Dyalog's github: https://github.com/Dyalog/ride

Full program on GitHub.

Full program including code to deal with heaps, on GitHub.

Program I used for the above results

See my solution on GitHub.

Note also that you can solve this without a complexity dependency on n. Most solutions I have seen, including mine run in time O(tD), where t is the maximum value of a timer, and D the number of generation, requiring O(t) memory. (This is assuming we can do the required arithmetic operations in constant time, and each numbers require a fixed around of memory storage; if the number of fish gets huge, throw in an additional log n in the complexities, where n is the number of fish on the final day).

Based on my matrix exponentiation solution, here is a closed-form solution:

In my Perl solution of today (I assume, you mean 2021, Day 4), I read stuff in paragraph mode ($/ = "") which makes Perl split input on 2 or more newlines.

I considered doing that for my (Perl) solution, but given the cards are small, that seemed overkill.

Python implementation on GitHub