advent-of-code/2023/1/Main.hs

{-# LANGUAGE TupleSections #-}

import           Data.Char (isDigit, digitToInt)
import           Data.Function (on)
import           Data.List (tails, findIndex, isPrefixOf, minimumBy)
import           Data.Maybe (mapMaybe)
import           Data.Bifunctor (first, bimap)

type LineOp = String -> Int

wordMap :: [(String, Int)]
wordMap = [ ("one", 1)
          , ("two", 2)
          , ("three", 3)
          , ("four", 4)
          , ("five", 5)
          , ("six", 6)
          , ("seven", 7)
          , ("eight", 8)
          , ("nine", 9)]

fullWordMap :: [(String, Int)]
fullWordMap = wordMap ++ (zip =<< map show) [1 .. 9]

opLineBasic :: LineOp
opLineBasic l =
  (combineDigits `on` ($ digitToInt <$> filter isDigit l)) head last

firstNumInLine :: String -> [(String, Int)] -> Int
firstNumInLine l = fst . minimumBy (compare `on` snd) . mapMaybe numIndex
  where
    numIndex (str, num) = (num, ) <$> findIndex (isPrefixOf str) (tails l)

opLineAdvanced :: LineOp
opLineAdvanced l = (combineDigits `on` uncurry firstNumInLine)
  <*> bimap reverse (map $ first reverse)
  $ (l, fullWordMap)

combineDigits :: Int -> Int -> Int
combineDigits = (+) . (10 *)

opLines :: [String] -> Int
opLines = sum . map opLineAdvanced

main :: IO ()
main = do
  content <- readFile "data.txt"
  print . opLines . lines $ content