Day 19, Part 1

adventofcode2024.cabal

@@ -67,3 +67,4 @@ executable adventofcode2024
     Day17.Puzzle1
     Day18.Puzzle1
     Day18.Puzzle2
+    Day19.Puzzle1

src/Day19/Puzzle1.hs

@@ -0,0 +1,31 @@
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
+module Day19.Puzzle1 (day19_1) where
+
+import Control.Monad (guard)
+import Data.List (isPrefixOf)
+import Data.List.Split (splitOn)
+
+getDesignCombinations :: String -> [String] -> String -> [String]
+getDesignCombinations design towels cur = do
+  towel <- towels
+  guard $ towel `isPrefixOf` design
+
+  let design' = drop (length towel) design
+  if null design'
+    then return $ drop 1 cur
+    else getDesignCombinations design' towels (cur ++ "," ++ towel)
+
+isDesignPossible :: String -> [String] -> Bool
+isDesignPossible design towels =
+  let combinations = getDesignCombinations design towels ""
+   in (not . null) combinations
+
+day19_1 :: IO ()
+day19_1 = do
+  contents <- lines <$> readFile "input/day19.txt"
+  let [[ts], designs] = splitOn [""] contents
+      towels = splitOn ", " ts
+  putStrLn $
+    "Day 19, Puzzle 1 solution: "
+      ++ show (length . filter id $ map (`isDesignPossible` towels) designs)

src/Main.hs

@@ -30,6 +30,7 @@ import Day15.Puzzle1
 import Day17.Puzzle1
 import Day18.Puzzle1
 import Day18.Puzzle2
+import Day19.Puzzle1
 import System.Environment (getArgs)
 
 main :: IO ()
@@ -66,4 +67,5 @@ main = do
     "17" : "1" : _ -> day17_1
     "18" : "1" : _ -> day18_1
     "18" : "2" : _ -> day18_2
+    "19" : "1" : _ -> day19_1
     _ -> error "Not implemented"