advent01/Main.hs

   1 -- Writeup at https://work.njae.me.uk/advent-of-code-2023-day-01/
   2
   3 import AoC
   4 import Data.Char
   5 import Data.List
   6 import Data.List.Split
   7
   8
   9 main :: IO ()
  10 main =
  11   do  dataFileName <- getDataFileName
  12       cals <- readFile dataFileName
  13       let calibrations = lines cals
  14       print $ part1 calibrations
  15       print $ part2 calibrations
  16
  17 part1 :: [String] -> Int
  18 -- part1 calibrations = sum $ fmap getCalibration calibrations
  19 part1  = sum . (fmap getCalibration)
  20
  21 part2 :: [String] -> Int
  22 part2 calibrations = sum $ fmap (getCalibration . replaceNums) calibrations
  23
  24 getCalibration :: String -> Int
  25 getCalibration calibration = read [head digits, last digits]
  26   where digits = filter isDigit calibration
  27
  28 replaceNums :: String -> String
  29 replaceNums [] = []
  30 replaceNums haystack
  31   | "one"   `isPrefixOf` haystack = '1' : remainder
  32   | "two"   `isPrefixOf` haystack = '2' : remainder
  33   | "three" `isPrefixOf` haystack = '3' : remainder
  34   | "four"  `isPrefixOf` haystack = '4' : remainder
  35   | "five"  `isPrefixOf` haystack = '5' : remainder
  36   | "six"   `isPrefixOf` haystack = '6' : remainder
  37   | "seven" `isPrefixOf` haystack = '7' : remainder
  38   | "eight" `isPrefixOf` haystack = '8' : remainder
  39   | "nine"  `isPrefixOf` haystack = '9' : remainder
  40   | otherwise = (head haystack) : remainder
  41   where remainder = replaceNums $ tail haystack
  42