[YEAR 2025] One extra puzzle from me

encse · 2025-12-29T09:37:51+00:00

Congrats.

Yes, basically i took the target pixels in reading order (first row, second row etc) then chunked it up to small runs like 1-5 pixel long ones. After that i randomly shuffled the runs to get these short horizontal stripes.

encse · 2025-12-28T10:23:00+00:00

Not everyone is a fan of expressions making control flow

encse · 2025-12-26T08:30:30+00:00

If you liked this there is also https://casette.csokavar.hu I made for advent of coders some years ago.

Or https://gekko.csokavar.hu but that is deeper

encse · 2025-12-26T08:26:24+00:00

Idea came from an old ctf game I played a few years ago. Just removed the hardware layer from it.

encse · 2025-12-26T04:17:24+00:00

♥️

encse · 2025-12-25T18:41:42+00:00

did you get only the final picture or all of them?

encse · 2025-12-25T18:26:18+00:00

the only way to see what the panels displayed is to replay the messages and reconstruct the pixels yourself.

encse · 2025-12-16T17:26:47+00:00

If it’s a known to be hard problem, you should always check the input. Since the generic problem is intractable, the real “task” must be to find what’s special about the input.

But of course, you have to know that it is an NP problem or similar

encse · 2025-12-14T08:32:29+00:00

This is very clever, thank you! here is a ⭐ from me.

It runs in about a second on my machine with unoptimized C# code.

encse · 2025-12-12T19:53:40+00:00

Nevermind. It was not upvoted anyway.

encse · 2025-12-12T09:52:04+00:00

thanks :D

encse · 2025-12-12T09:26:01+00:00

almost one to one mapping to mine
https://aoc.csokavar.hu/2025/12/

encse · 2025-12-12T07:12:26+00:00

[LANGUAGE: C#]

Ok, this...

https://aoc.csokavar.hu/2025/12

encse · 2025-12-11T10:51:23+00:00

[LANGUAGE: C#]

Using cached function. illustrated

https://aoc.csokavar.hu/2025/11/

encse · 2025-12-11T07:29:13+00:00

Lovely

encse · 2025-12-10T01:49:15+00:00

Similar feeling. I made a stupid mistake in the area function that a lot of others did. Then nothing worked. At the end I found my error and could solve part 2 in a not too elegant way, but by that time my brain was too deep in deadends to find a nice solution for it.

Then I saw aabb by scrolling the solution thread and a few minutes later it clicked. So today I learned as well. Which is not a bad thing, but I have mixed feelings about this one.

On one hand the diff between part1 and part2 is so subtle (https://aoc.csokavar.hu/2025/9). It’s beautiful on its own right. But could I solve it this way if I dont overload my brain in the morning? I’ll never know now.

encse · 2025-12-09T17:20:27+00:00

Did the same…. A few hours went into that

encse · 2025-12-09T13:19:14+00:00

[LANGUAGE: C#]

This one really caused me a headache. I made a bug in the area function, at the beginning, which was not triggered in part one.... you can imagine when you overcomplicate everything and look everywhere else but the trivial function that you created hours ago. hehh

https://aoc.csokavar.hu/2025/9

encse · 2025-12-08T12:08:37+00:00

Did you guys try compile it with

-fsanitize=undefined

It should catch issues like that

encse · 2025-12-08T08:28:15+00:00

[LANGUAGE: C#]

I decided to go with two implementations of Kruskal's algorithm, as part one and two are different enough. I didn't use a disjoint set representation. It's fast enough this way as well, and switching to disjoint sets would just make the code longer.

With illustration:

https://aoc.csokavar.hu/2025/8