2016, Day 18

Author: chenson2018

2016/18/haskell/18.hs

@@ -0,0 +1,10 @@
+iter xs = aux ('.' : xs ++ ".")
+  where
+    aux (a : b : c : xs) = (if a == c then '.' else '^') : aux (b : c : xs)
+    aux _ = []
+
+main = do
+  let input = "^.^^^.^..^....^^....^^^^.^^.^...^^.^.^^.^^.^^..^.^...^.^..^.^^.^..^.....^^^.^.^^^..^^...^^^...^...^."
+  let rows = iterate iter input
+  print $ length $ filter (== '.') $ concat $ take 40 rows
+  print $ length $ filter (== '.') $ concat $ take 400000 rows