adventofcode1701/app/advent01verbose.hs

   1 {-# LANGUAGE NegativeLiterals #-}
   2
   3 module Main(main) where
   4
   5 import Data.List (tails)
   6
   7 main :: IO ()
   8 main = do
   9         digits <- readFile "data/advent01.txt"
  10         print $ part1 digits
  11         print $ part2 digits
  12
  13 part1 :: String -> Integer
  14 part1 = sum_valid_pairs . part1_extract
  15
  16 part2 :: String -> Integer
  17 part2 = sum_valid_pairs . part2_extract
  18
  19 part1_extract :: String -> [String]
  20 part1_extract digits =  map (take 2) $ tails (digits ++ [head digits])
  21
  22 part2_extract :: String -> [String]
  23 part2_extract digits = map (\ds -> (take 1 ds) ++ (take 1 $ drop offset ds))
  24         $ take (length digits)
  25         $ tails (digits ++ digits)
  26     where offset = length digits `div` 2
  27
  28 sum_valid_pairs :: [String] -> Integer
  29 sum_valid_pairs possibles = sum $ map (read . take 1)
  30                    $ filter (\(x:y:_) -> x == y)
  31                    $ filter (\p -> length p == 2) possibles
  32