Getting an intractable problem, and not solving it.

Time for some standard graph algorithms.

Attempting to use libraries to solve part 2, and finding nothing quite worked.

Getting the right solution, but much too slowly.

Union-find makes it easy.

Sets, multisets, and not needing complex type declarations.

I started with parsing, then ended up with string munging until it looked right.

Another day where writing down the definitions is most of the solution.

Thinking functionally saves the day.