Day 23

It's not my proudest work, but it gets the answer in 15 seconds or less on my machine which, while far slower than pretty much any other day, is a huge improvement over my initial attempts that took 30+ minutes. There is a lot of low-hanging fruit that could be used to improve this runtime, mostly around filtering possible moves and the Amphipod hashing function for memoization, but I am spending that time prepping for day 24 (and eventually finishing day 21 part 2...).

My "coordinate" system is hideous and I feel bad about it, as is my handling of part 2 vs part 1 w.r.t. adding two new rows. But I didn't want to manufacture some kind of 2d grid that had a bunch of closed-off spaces, so I just made this awful thing work instead. I have an easier time thinking in discrete "1d" chunks than I do thinking in 2d graphs anyway. I would also love to add a stack to be able to replay the moves that got us to a solution, but again, I'm trying to move on! :)

advent-of-code-2021.csproj

@@ -84,6 +84,9 @@
 	  <None Update="inputs\22.txt">
 	    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
 	  </None>
+	  <None Update="inputs\23.txt">
+	    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+	  </None>
 	</ItemGroup>
 
 </Project>