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    1 {-|
    2 Module:      Y2015.D02
    3 Description: Advent of Code Day 02 Solutions.
    4 License:     MIT
    5 Maintainer:  @tylerjl
    6 
    7 Solutions to the day 02 set of problems for <adventofcode.com>.
    8 -}
    9 module Y2015.D02
   10   ( Present(..)
   11   , parsePresents
   12   , surfaceArea
   13   , ribbonLength
   14   ) where
   15 
   16 import Data.Attoparsec.Text hiding (take)
   17 import Data.List (foldl', sort)
   18 import Data.Text (Text)
   19 
   20 -- |Represents a present in three dimensions
   21 data Present =
   22   Present Int
   23           Int
   24           Int
   25   deriving (Eq, Show)
   26 
   27 presentsParser :: Parser [Present]
   28 presentsParser = many1 (presentParser <* skipMany endOfLine)
   29 
   30 presentParser :: Parser Present
   31 presentParser =
   32   Present <$> (decimal <* char 'x') <*> (decimal <* char 'x') <*> decimal
   33 
   34 -- |Parse presents from an input string
   35 parsePresents
   36   :: Text -- ^ Raw input of present dimensions
   37   -> Maybe [Present] -- ^ Possible list of 'Present's
   38 parsePresents s =
   39   case parseOnly presentsParser s of
   40     Right ps -> Just ps
   41     Left _ -> Nothing
   42 
   43 -- |Find total surface area from list of 'Present's
   44 surfaceArea
   45   :: [Present] -- ^ List of 'Present's
   46   -> Int -- ^ Total surface area of all 'Present's
   47 surfaceArea = foldl' (+) 0 . map wrapping
   48 
   49 wrapping :: Present -> Int
   50 wrapping p = sqft p + product (smallest p)
   51 
   52 smallest :: Present -> [Int]
   53 smallest (Present l w h) = take 2 $ sort [l, w, h]
   54 
   55 sqft :: Present -> Int
   56 sqft (Present l w h) = 2 * l * w + 2 * w * h + 2 * h * l
   57 
   58 area :: Present -> Int
   59 area (Present l w h) = l * w * h
   60 
   61 -- |Find required length of ribbon for a list of presents.
   62 ribbonLength
   63   :: [Present] -- ^ List of 'Present's
   64   -> Int -- ^ Total length of required ribbon
   65 ribbonLength = sum . map presentRibbon
   66 
   67 presentRibbon :: Present -> Int
   68 presentRibbon p = sum (map (* 2) $ smallest p) + area p