[tialaramex]

I don't necessarily mind these "reverse engineering" type problems, I think you can consider your input part of the problem statement. In earlier years it was common, particularly in early days, for your input to be on the page itself IIRC, like "Your input is 103053439" rather than a link.

One thing that bothers me more though is when the example input is nonsense for Part II or can be solved but in a radically different way because it has very different properties than the inputs people are given for real. Contrast day 19, where the example input has a rational answer, which you are told about for the Part II, against day 20 where the example input is completely irrelevant for Part II and good luck.

[epiccoleman]

Yeah, it's always rough when you write a solution for part 2, and it passes all the samples, but then has issues with the real input.

One thing I've tried to do when I run into those kinds of problems is to write a little benchmark to illustrate the difference between approaches. It's always kinda fun to watch your initial brute force solution start chugging while your shiny new solution seems to handle whatever you toss at it - great lesson in choosing effective algorithms.

I use Elixir to do the puzzles, so I've used Benchee for this, and it works very well. So easy to set up too.

Here's an example benchmark, which also has the output. As the input size increases you start getting some pretty crazy ratios between the two algorithms (the "smart" version was 200,000 times faster than the "naive" one on the largest test input!)

https://github.com/epiccoleman/advent_of_code_ex/blob/master...

[Jare]

> I think you can consider your input part of the problem statement

That would be fine if there was only one input. But we have seen countless cases of a solution working for some and not others (including/especially the test input). So the cases and patterns I see in my input may be part of the hidden problem statement, or they may be just an artifact of my particular input. I at least feel more satisfied when I know my solution will solve all inputs.

For that reason, I side with the desire for a bit more purity and closure, vs having to guess, and not being sure about your guess until you go to reddit. Making educated guesses about patterns is a valuable ability, but I don't like the aesthetics of it here.

[tialaramex]

This is definitely something where tastes vary, for example you can see below several people assumed you can multiply any numbers, and that actually worked because the numbers are co-prime, but strictly you need LCM (and since I had LCM in my toolkit I used it)

I try to write solutions which would work for inputs like mine but I'm not fussed if, for example, my code panics on hypothetical "valid" inputs that I didn't consider.

So e.g I have panics for nonsense input like, "Pipe networks with more than one Start can't be solved" and "Uneveen seed list cannot work as described in problem" [Yes that's a typo] but I also have "Should not send signals unexpectedly" and "Surely not all the stones have X velocity 0"