2023 day 9

2023/9/Main1.hs

@@ -0,0 +1,12 @@
+import Data.List.Split (splitOn)
+
+solve :: [Int] -> Int
+solve [] = 0
+solve xs@(x:_) = x + solve (getDifferences xs)
+  where
+    getDifferences = zipWith (-) <*> tail
+
+main :: IO ()
+main = print . sum . map solveLine . lines =<< readFile "data.txt"
+  where
+    solveLine = solve . reverse . map read . splitOn " "

2023/9/Main2.hs

@@ -0,0 +1,12 @@
+import Data.List.Split (splitOn)
+
+solve :: [Int] -> Int
+solve [] = 0
+solve xs@(x:_) = x + solve (getDifferences xs)
+  where
+    getDifferences = zipWith (-) <*> tail
+
+main :: IO ()
+main = print . sum . map solveLine . lines =<< readFile "data.txt"
+  where
+    solveLine = solve . map read . splitOn " "

flake.nix

@@ -32,6 +32,7 @@
             (pkgs.ghc.withPackages (p:
               with p; [
                 containers
+                extra
                 regex-compat
                 split
                 unordered-containers