There were two issues here:
1. Searches for a subset would overlap a found area. So if the search string was R,4,R,4 and the string was R,4,R,4,R,4, it would say there were 2 matches in there since it re-used the middle set.
2. It would happily find a subset that was too long. 20 characters is the maximum program length, per the instructions. Huge thanks to the intcode program for having this as a diagnostic message.
Now this can solve both input sets I have access to.
It works for one of my account's inputs, but not the other. At least the foundation is in place...just need to fix the heuristics for determining which subsets to hang onto.
I also desperately need to clean up this code as I was writing it just to get stuff working and not thinking about actual structure.
The last remaining bit is to scan the instructions array for groups of consecutive entries. My current plan is to start with probably 4 instructions and scan forward for the same consecutive set occurring again; if the count of other occurrences ever dips below 3, drop the most recently added set of 2 and pull the remaining entries into program A. Then repeat for programs B and C, and check that the list of instructions is now empty. Finally, compare each chunk successively to the full string of instructions to produce some combination of A,B,Cs to satisfy the requirements, and feed all that into the program's inputs.
