AdventOfCode2023-Haskell/day4/app/Main.hs

module Main where

import Data.HashSet (HashSet)
import qualified Data.HashSet as HS
import Data.List.Split (splitOn)

partOne :: String -> Int
partOne = sum . map computePoints . filter (not . null) . map partOnePerLine . lines

partOnePerLine :: String -> [Int]
partOnePerLine = hashIntersect . strToInt . beforeHashSet

computePoints :: [Int] -> Int
computePoints n = 2 ^ (length n - 1)

hashIntersect :: (HashSet Int, HashSet Int) -> [Int]
hashIntersect (x, y) = HS.toList (HS.intersection x y)

strToInt :: (String, String) -> (HashSet Int, HashSet Int)
strToInt (win, cards) = ((HS.fromList . map getInt . words) win, (HS.fromList . map getInt . words) cards)

getInt :: String -> Int
getInt n = read n :: Int

beforeHashSet :: String -> (String, String)
beforeHashSet = (\v -> (head v, last v)) . splitOn "|" . last . splitOn ":"

partTwoPerLine :: String -> Int
partTwoPerLine = length . partOnePerLine

main :: IO ()
main = do
  content <- readFile "sample.txt"
  (print . partOne) content
  let tmp = (zip [1 ..] . map partTwoPerLine . lines) content
  mapM_ print tmp