day 5

5/solution.hs

@@ -0,0 +1,70 @@
+import Data.List
+import qualified Data.List.Split as S
+import Debug.Trace
+
+data PageNum = Page Integer [(Integer, Integer)]
+
+instance Num PageNum where
+    (Page x r) + (Page y _) = Page (x+y) r
+    (Page x r) - (Page y _) = Page (x-y) r
+
+instance Eq PageNum where
+    (Page x _) == (Page y _) = x == y
+
+instance Ord PageNum where
+    (Page a zs) <= (Page b _) = foldl (&&) True $ map (\x -> checkRule x [a, b])  zs
+
+instance Show PageNum where
+    show (Page a _) = "Page " ++ (show a)
+
+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
+
+toTuple :: [a] -> (a, a)
+toTuple (x:(y:ys)) = (x, y)
+
+fromTuple :: (a, a) -> [a]
+fromTuple (x, y) = [x, y]
+
+splitInput :: String -> [(Integer, Integer)]
+splitInput text = map (\x -> toTuple $ map read x) $ map (filter (/="")) $ map (split ['|']) $ split ['\n'] text
+
+splitInput2 :: String -> [[Integer]]
+splitInput2 text = map (\x -> map read x) $ map (filter (/="")) $ map (split [',']) $ split ['\n'] text
+
+checkRule :: (Integer, Integer) -> [Integer] -> Bool
+checkRule _ [] = True
+checkRule (a, b) (x:xs) 
+  | a == x              = True
+  | b == x && elem a xs = False
+  | b == x              = True
+  | otherwise           = checkRule (a, b) xs
+
+solve1 :: [(Integer, Integer)] -> [[Integer]] -> Integer
+solve1 [] y = sum $ map (\x -> x!!(div ((length x)-1) 2)) y
+solve1 (x:xs) y = solve1 (xs) (filter (\y -> checkRule x y) y)
+
+solve2 :: [(Integer, Integer)] -> [[Integer]] -> PageNum
+solve2 a [] = Page 0 a
+solve2 rules (x:xs) = (getMid $ sort $ map (\a -> Page a rules) x) + (solve2 rules xs)
+
+getMid :: [a] -> a
+getMid xs = xs !! (div ((length xs) -1) 2)
+
+main :: IO()
+main = do
+       fileinp <- readFile "input.txt"
+       let sections = S.splitOn "\n\n" fileinp
+       let parsed = splitInput (sections!!0)
+       let parsed2 = splitInput2 (sections!!1)
+       let solved1 = solve1 parsed parsed2
+       let solved2 = (solve2 parsed parsed2) - (Page solved1 [])
+       print solved1
+       print solved2