Advent Of Code

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An unofficial home for the advent of code community on programming.dev!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

AoC 2023

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☃️ - 2023 DAY 11 SOLUTIONS - ☃️ (programming.dev)

submitted 11 months ago* (last edited 11 months ago) by [email protected] to c/[email protected]

19 comments fedilink hide all child comments

Day 11: Cosmic Expansion

Megathread guidelines

Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
Code block support is not fully rolled out yet but likely will be in the middle of the event. Try to share solutions as both code blocks and using something such as https://topaz.github.io/paste/ , pastebin, or github (code blocks to future proof it for when 0.19 comes out and since code blocks currently function in some apps and some instances as well if they are running a 0.19 beta)

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What is this?: Here is a post with a large amount of details: https://programming.dev/post/6637268
Where do I participate?: https://adventofcode.com/
Is there a leaderboard for the community?: We have a programming.dev leaderboard with the info on how to join in this post: https://programming.dev/post/6631465

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[–] [email protected] 12 points 11 months ago* (last edited 11 months ago) (1 children)

Man this one frustrated me because of a subtle difference in the wording of part 1 vs part 2. I had the correct logic from the start, but with an off-by-one error because of my interpretation of the wording. Part 1 says, "any rows or columns that contain no galaxies should all actually be twice as big" while part 2 says, "each empty column should be replaced with 1000000 empty columns".

I added 1 column/row in part 1, and 1_000_000 in part 2. But if you're replacing an empty column with 1_000_000, you're actually adding 999_999 columns. It took me a good hour to discover where that off-by-one error was coming from.

[–] zarlin 4 points 11 months ago (1 children)

Yepp, this one got me as well! I found the discrepancy when testing against the sample through, which showed the result for a factor 100 (which needed to be 99). Knowing the correct outcome made debugging a lot easier.

I always make sure my solution passes all the samples before trying the full input.

[–] [email protected] 4 points 11 months ago (1 children)

Me too. I ran all the samples, and I was still banging my head. I can usually see the mistake if it's an off-by-one error in a calculation, but this was a mistake in reading the problem description, so I couldn't see it at first.

[–] zarlin 2 points 11 months ago

Yeah the descriptions contain a lot of story fluff, but also critical bits of information.