<Advent of Code 2024 day 17> (no spoilers) :thread...

# advent-of-code

[Advent of Code 2023 day 17]

Advent of Code 2024 day 17 (no spoilers) 🧵

[Dan Fingal-Surma]

I see one obvious pattern in the output but it is not narrowing the range of registers to check enough

[Dan Fingal-Surma]

Am I supposed to be able to reverse the execution of the program from the output?

[Jonathan Kolberg]

I thought about that too, but did not want to do it, for my input every execution stops after <100 steps in the simulation, I'm brute forcing atm. My estimates say I need ~1h to try all.

[Dan Fingal-Surma]

I don’t think your estimate is correct. What range are you brute forcing over.

[Jonathan Kolberg]

All positiv integers, so (0..Int.MAX_VALUE), to be honest, I'm kinda tired to detect cycles or reverse compute the program.

[Dan Fingal-Surma]

your estimate is not correct 😞

[Norbert Kiesel]

For me, no positive integer produces the solution. Thus, looks like it's a Long

[Norbert Kiesel]

And btw: testing all positive Int takes me less than 2.5 minutes

[Dan Fingal-Surma]

It is a long, yes. We are discussing how to solve it in the spoiler thread

[Dan Fingal-Surma]

No one has solved it yet

[Dan Fingal-Surma]

On here

[Dan Fingal-Surma]

OK it’s been solved

[Dan Fingal-Surma]

By @Michael de Kaste

[Sergei Petunin]

Anyone got any stupid/obvious bugs from part1 to share? My solution passes the sample and all examples provided in the text, but produces wrong result on my own input 😢

[Fredrik Rødland]

@Sergei Petunin might want to look into bdv (commenting my impl of bdv out makes test and other examples still work but real input fail)

[Pawel Matysek]

@Sergei Petunin read carefully about the difference between literal operand and combo operand it was my bug 😉

[Pawel Matysek]

and about part2: I've tried already 0..Int.MAX_VALUE range, now I'm running Int.MAX_VALUE..Long.MAX_VALUE and if it does not produce a result till 16 I will try something different 😅

[Sergei Petunin]

@Fredrik Rødland same for me, but it looks like I don't even have bdv in my input 😕

[Sergei Petunin]

(The numerator is still read from the A register.)

aaaaargh

[Sergei Petunin]

thanks, folks

[Luan Tran]

Any hints on the solution to part 2? Brute Force or Reverse it?

[Dan Fingal-Surma]

You cannot brute force it

[Dan Fingal-Surma]

You must understand what the program is doing

[Dan Fingal-Surma]

To some degree

[Jonathan Kolberg]

Yeah brute forcing it did not work out, had to understand what is really happening.

[Jaap Beetstra]

As much difficulty as I had solving this, I do like that the result included this little code snippet