haskell: 2015 03

2015/haskell/app/Main.hs

@@ -2,7 +2,7 @@ module Main where
 
 import Text.Printf (printf)
 import qualified Day01
-
+import qualified Day03
 
 readDay :: Int -> IO String
 readDay n = readFile $ getPath n
@@ -12,7 +12,7 @@ readDay n = readFile $ getPath n
 
 main :: IO ()
 main = do
-  content <- readDay 1
-  let parsed = Day01.parse content
-  print $ Day01.solve1 parsed
-  print $ Day01.solve2 parsed
+  content <- readDay 3
+  let parsed = Day03.parse content
+  print $ Day03.solve1 parsed
+  print $ Day03.solve2 parsed

2015/haskell/haskell.cabal

@@ -19,7 +19,9 @@ maintainer:         maciej@kamoshi.org
 extra-source-files: CHANGELOG.md
 
 library
-    exposed-modules:  Day01
+    exposed-modules:
+      Day01
+      Day03
 
     -- Modules included in this library but not exported.
     -- other-modules:

2015/haskell/src/Day03.hs

@@ -0,0 +1,34 @@
+module Day03 (parse, solve1, solve2) where
+
+import Data.List (nub, partition)
+
+
+data Move = L | R | U | D deriving Show
+
+parse :: String -> [Move]
+parse = map mapper
+  where
+    mapper c = case c of
+      '<' -> L
+      '>' -> R
+      '^' -> U
+      'v' -> D
+
+findPath :: [Move] -> [(Int, Int)]
+findPath = scanl move (0, 0)
+  where
+    move (x, y) dir = case dir of
+      L -> (x-1, y)
+      R -> (x+1, y)
+      U -> (x, y+1)
+      D -> (x, y-1)
+
+solve1 :: [Move] -> Int
+solve1 = length . nub . findPath
+
+solve2 :: [Move] -> Int
+solve2 moves =
+  let (xs, ys) = partition (even . fst) $ zip [0..] moves
+  in length . nub $ findPath' xs <> findPath' ys
+    where
+      findPath' = findPath . map snd

2015/haskell/src/MyLib.hs

@@ -1,4 +0,0 @@
-module MyLib (someFunc) where
-
-someFunc :: IO ()
-someFunc = putStrLn "someFunc"