alternative day 11 solution in Haskell

Author: Andriamanitra

day11/solution.hs

@@ -0,0 +1,25 @@
+import Data.List (transpose)
+
+countGalaxies = length . filter ('#'==)
+
+sumDistances mul galCounts =
+  let
+    f 0 l r = mul * l * r
+    f _ l r = l * r
+    left = scanl (+) 0 galCounts
+    right = scanr (+) 0 galCounts
+  in
+    sum $ zipWith3 f galCounts left right
+
+main = do
+  input <- lines <$> getContents
+  let galaxiesByRow = map countGalaxies input
+  let galaxiesByCol = map countGalaxies (transpose input)
+
+  putStrLn "Part 1:"
+  let part1 = sumDistances 2
+  print $ part1 galaxiesByRow + part1 galaxiesByCol
+
+  putStrLn "Part 2:"
+  let part2 = sumDistances 1_000_000
+  print $ part2 galaxiesByRow + part2 galaxiesByCol