initialise repo; add days 1-3

01/solution.hs

@@ -0,0 +1,56 @@
+import Debug.Trace
+import Data.Maybe
+
+traceOut :: Show a => a -> a
+traceOut x = traceShow x x
+
+data Shift = Shift Int
+
+instance Show Shift where
+    show (Shift x) = show x
+
+addFirst :: [[a]] -> a -> [[a]]
+addFirst [] x = [[x]]
+addFirst (y:ys) x = ([x] ++ y) : ys
+
+split :: [Char] -> [Char] -> [[Char]]
+split _ [] = []
+split delims (x:xs)
+  | elem x delims = [[]] ++ split delims xs
+  | otherwise     = addFirst (split delims xs) x
+
+iterateFrom :: [a -> a] -> a -> [a]
+iterateFrom [] x = [x]
+iterateFrom (f:fs) x = x : (iterateFrom fs (f x))
+
+iterateWith :: (a -> b -> b) -> [a] -> b -> [b]
+iterateWith f [] b = [b]
+iterateWith f (a:as) b = b : iterateWith f as (f a b)
+
+parseShift :: String -> Maybe Shift
+parseShift ('L':xs) = Just $ Shift (-(read xs))
+parseShift ('R':xs) = Just $ Shift (read xs)
+parseShift _ = Nothing
+
+parseFile :: String -> Maybe [Shift]
+parseFile = sequence . map parseShift . split ['\n']
+
+toFunc :: Shift -> (Int -> Int)
+toFunc (Shift x) = (+x)
+
+solve1 :: [Shift] -> Int
+solve1 shifts = length $ filter (==0) $ map (`mod` 100) $ iterateFrom (map toFunc shifts) 50
+
+expandShift :: Shift -> [Shift]
+expandShift (Shift x) = take (abs x) $ repeat (Shift (signum x))
+
+solve2 :: [Shift] -> Int
+solve2 = solve1 . foldl (++) [] . map expandShift
+
+main = do 
+    fileinp <- readFile "input.txt"
+    let shifts = fromJust $ parseFile fileinp
+    let solved1 = solve1 shifts
+    let solved2 = solve2 shifts
+    print solved1
+    print solved2