Day 7, Part 1

Day7/puzzle1.hs

@@ -0,0 +1,19 @@
+import Data.List (transpose)
+import Data.List.Split (splitOn)
+
+type Equation = (Int, [Int])
+
+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)
+
+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