Refactor code

src/Day07.hs

@@ -0,0 +1,56 @@
+module Day07
+  ( day07_1,
+    day07_2,
+  )
+where
+
+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
+isSolvable cur (result, x : y : ys) =
+  isSolvable (cur + x + y) (result, ys)
+    || isSolvable ((cur + x) * y) (result, ys)
+    || isSolvable (cur * x + y) (result, ys)
+    || isSolvable (cur * x * y) (result, ys)
+
+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)
+
+day07_1 :: IO ()
+day07_1 = do
+  [x, y] <- transpose . map (splitOn ":") . lines <$> readFile "input/day7.txt"
+  let results = map read x
+      values = map read <$> map words y
+      equations = zip results values
+  putStrLn $
+    "Day 7, Puzzle 1 solution: "
+      ++ show (sum . map fst $ filter (isSolvable 0) equations)
+
+day07_2 :: IO ()
+day07_2 = do
+  [x, y] <- transpose . map (splitOn ":") . lines <$> readFile "input/day7.txt"
+  let results = map read x
+      values = map read <$> map words y
+      equations = zip results values
+  putStrLn $
+    "Day 7, Puzzle 2 solution: "
+      ++ show (sum . map fst $ filter (isSolvable' 0) equations)