advent03.hs

   1 module Main(main) where
   2
   3 import Data.List (transpose, sort)
   4 import Data.List.Split (splitOn, chunksOf)
   5
   6 type Triple = [Integer]
   7
   8 main :: IO ()
   9 main = do
  10         instrText <- readFile "advent03.txt"
  11         let triangles = map (parseLine) $ lines instrText
  12         part1 triangles
  13         part2 triangles
  14
  15
  16 part1 :: [Triple] -> IO ()
  17 part1 triangles = do
  18     print $ length $ filter (validTriangle) triangles
  19
  20 part2 :: [Triple] -> IO ()
  21 part2 triangles = do
  22     print $ length $ filter (validTriangle) $ byColumns triangles
  23
  24
  25 parseLine :: String -> Triple
  26 parseLine = map (read) . filter (not . null) . splitOn " "
  27
  28 validTriangle :: Triple -> Bool
  29 validTriangle triple = sortedTriple!!0 + sortedTriple!!1 > sortedTriple!!2
  30     where sortedTriple = sort triple
  31
  32 byColumns :: [[Integer]] -> [Triple]
  33 byColumns = chunksOf 3 . concat . transpose