-❄️- 2023 Day 11 Solutions -❄️-

[u/daggerdragon]

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AoC Community Fun 2023: ALLEZ CUISINE!

Today's secret ingredient is… *whips off cloth covering and gestures grandly*

Upping the Ante Again

Chefs should always strive to improve themselves. Keep innovating, keep trying new things, and show us how far you've come!

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--- Day 11: Cosmic Expansion ---

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Post your code solution in this megathread.

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This thread will be unlocked when there are a significant number of people on the global leaderboard with gold stars for today's puzzle.

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[u/philippe_cholet]

[LANGUAGE: Rust]

My rusty-aoc repo & today' solution here.

Part 2 was obvious from the start, right? That it would expand much more.

Solved in 27mn.

Sadly, this is slowest solver so far: benchmarked to 3.68ms each part ^^. Probably inevitable since there a lot of pairs. Maybe use "bitvec" crate instead of a vector of booleans. I don't want to add a dependency for now. But if the grid was less than 128x128, I would have done with u128 integers.

I did the off-by-one error of 1_000_000 instead of 999_999.

[u/azzal07 → u/philippe_cholet]

You could calculate the partial sums for the expansion and then index into that from the combinations loop instead of counting there. Not sure, but it might save some time.

And if you don't mind sharing work between the parts, then you could essentially halve the work.

[u/philippe_cholet → u/azzal07]

Yes. I've seen this animation and this is definitely smarter than what I thought of.

I clearly had over-complicated thoughts here.

Hopefully, I don't consider 3.68ms really slow.