Parser Combinators Beat Regexes

You can also use simple string search functions for this Advent of Code problem.

I used this approach for implementing orthography rules in a stenography application (implementing rules like `artistic + ly = artistically`) and in the benchmarks I did, a few lines of searching for character indexes was an order of magnitude faster than regexes. Each of my functions is about 3-10 ish lines of simple code compared to a 1-line regex.

You do have to handle cases like the character not being found, but I've had zero issues with the code and, in terms of what actually executes, it is vastly simpler. This is why the saying goes that if you make something twice as fast, you may have done something clever, but if you make it 10x faster, you stopped doing something dumb.

Basic string search and indexing operations (especially when there is language/library support for cheap spans) are definitely underappreciated.

I wouldn't reach for them as a first step though, because they'd take more automated tests to give me confidence of correctness, and most problems I end up solving are not CPU bound but programmer time bound.