import Data.List (transpose) import Data.List.Split (splitOn) type Equation = (Int, [Int]) concatInt :: Int -> Int -> Int concatInt x y = read $ show x ++ show y isSolvable :: Int -> Equation -> Bool isSolvable cur (result, []) = cur == result isSolvable cur (result, [x]) = cur + x == result || cur * x == result || cur `concatInt` x == result isSolvable cur (result, x:y:ys) = isSolvable (cur + x + y) (result, ys) || isSolvable ((cur + x) * y) (result, ys) || isSolvable ((cur + x) `concatInt` y) (result, ys) || isSolvable (cur * x + y) (result, ys) || isSolvable (cur * x * y) (result, ys) || isSolvable ((cur * x) `concatInt` y) (result, ys) || isSolvable ((cur `concatInt` x) + y) (result, ys) || isSolvable ((cur `concatInt` x) * y) (result, ys) || isSolvable ((cur `concatInt` x) `concatInt` y) (result, ys) main = do [x, y] <- transpose . map (splitOn ":") . lines <$> readFile "day7.txt" let results = map read x values = map read <$> map words y equations = zip results values print . sum . map fst $ filter (isSolvable 0) equations