day 13

13/example.txt

@@ -0,0 +1,15 @@
+Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279

13/solution.hs

@@ -0,0 +1,49 @@
+import qualified Data.List.Split as S
+import Data.List
+import Data.Matrix as M
+import Data.Ratio
+import Debug.Trace
+
+traceOut :: Show a => a -> a
+traceOut x = (traceShow x x)
+
+addFirst :: [[a]] -> a -> [[a]]
+addFirst [] x = [[x]]
+addFirst (y:ys) x = ([x] ++ y) : ys
+
+split :: [Char] -> String -> [String]
+split _ [] = []
+split delims (x:xs)
+  | elem x delims = [[]] ++ split delims xs
+  | otherwise     = addFirst (split delims xs) x
+
+splitInput :: [String] -> [[[Ratio Int]]]
+splitInput = map (map (map ((% 1) . read . last . split "+=") . split [',']). split ['\n'])
+
+solve1 :: [[[Ratio Int]]] -> Ratio Int
+solve1 [] = 0
+solve1 (x:xs) = (let a = (inverse $ M.transpose $ fromLists ([x!!0, x!!1])) in
+    case a of 
+        Left _ -> 0
+        Right matrix -> let b = matrix * (M.transpose $ fromLists [x!!2]) in if (all (\x -> denominator x == 1) b) then sum (multiplier*b) else 0 
+    ) + solve1 xs
+
+solve2 :: [[[Ratio Int]]] -> Ratio Int
+solve2 [] = 0
+solve2 (x:xs) = (let a = (inverse $ M.transpose $ fromLists ([x!!0, x!!1])) in
+    case a of 
+        Left _ -> 0
+        Right matrix -> let b = matrix * (M.transpose $ shift + fromLists [x!!2]) in if (all (\x -> denominator x == 1) b) then sum(multiplier*b) else 0 
+    ) + solve1 xs
+
+multiplier :: Matrix (Ratio Int) = fromLists [[3 % 1, 0], [0, 1 % 1]]
+shift :: Matrix (Ratio Int) = fromLists [[10000000000000 % 1, 10000000000000 % 1]]
+
+main :: IO()
+main = do
+       fileinp <- readFile "input.txt"
+       let parsed = splitInput $ S.splitOn "\n\n" fileinp
+       let solved1 = solve1 parsed
+       let solved2 = solve2 parsed
+       print (numerator $ solved1)
+       print (numerator $ solved2)