Added a version using

diff --git a/advent16i.hs b/advent16i.hs
new file mode 100644 (file)
index 0000000..4cf13f6
--- /dev/null
+++ b/advent16i.hs
@@ -0,0 +1,43 @@
+input = "11100010111110100"
+disk1length = 272
+disk2length = 35651584
+
+-- input = "10000"
+-- disk1length = 20
+
+main :: IO ()
+main = do 
+    part1 
+    part2
+
+part1 :: IO ()
+part1 = print $ fill disk1length input
+
+part2 :: IO ()
+part2 = print $ fill disk2length input
+
+fill :: Int -> String -> String
+fill len filler = deBool $ checksum $ take len $ expand len $ enBool filler
+
+enBool :: String -> [Bool]
+enBool = map (== '1')
+
+deBool :: [Bool] -> String
+deBool = map (\b -> if b then '1' else '0')
+
+
+expand :: Int -> [Bool] -> [Bool]
+expand len = head . dropWhile ((<= len) . length) . iterate expandStep
+
+expandStep :: [Bool] -> [Bool]
+expandStep a = a ++ [False] ++ b
+        where b = map (not) $ reverse a
+
+checksum :: [Bool] -> [Bool]
+checksum = head . dropWhile (even . length) . iterate checksumStep 
+
+checksumStep :: [Bool] -> [Bool]
+checksumStep [] = []
+checksumStep [x] = [x]
+checksumStep (x:y:xs) = (x==y):(checksumStep xs)
+