2024 day 1: Haskell solution

2024/1/Main1.hs

@@ -0,0 +1,11 @@
+import           Data.List (sort, transpose)
+import           Data.List.Split (splitOn)
+
+solve :: [[Int]] -> Int
+solve = sum . map abs . (\[x, xx] -> zipWith (-) x xx) . map sort
+
+main :: IO ()
+main =
+  print . solve . transpose . map parseLine . lines =<< readFile "data.txt"
+  where
+    parseLine = map read . filter (not . null) . splitOn " "

2024/1/Main2.hs

@@ -0,0 +1,14 @@
+import qualified Data.IntMultiSet as IMultiSet
+import           Data.List (sort, transpose)
+import           Data.List.Split (splitOn)
+
+solve :: [[Int]] -> Int
+solve [l, r] = sum $ map (\x -> x * IMultiSet.occur x rs) l
+  where
+    rs = IMultiSet.fromList r
+
+main :: IO ()
+main =
+  print . solve . transpose . map parseLine . lines =<< readFile "data.txt"
+  where
+    parseLine = map read . filter (not . null) . splitOn " "

flake.nix

@@ -33,6 +33,7 @@
               with p; [
                 containers
                 extra
+                multiset
                 regex-compat
                 split
                 text