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submitted 9 months ago* (last edited 9 months ago) by Ategon@programming.dev to c/advent_of_code@programming.dev

Day 11: Cosmic Expansion

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[-] SteveDinn@lemmy.ca 13 points 9 months ago* (last edited 9 months ago)

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@lemmy.world 4 points 9 months ago

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.

[-] SteveDinn@lemmy.ca 4 points 9 months ago

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@lemmy.world 2 points 9 months ago

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

this post was submitted on 11 Dec 2023
12 points (80.0% liked)

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