45 lines
1.3 KiB
Haskell
45 lines
1.3 KiB
Haskell
|
module Day3_1 where
|
||
|
|
import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
|
||
|
|
import Data.List ( maximumBy, minimumBy, group, sort )
|
||
|
|
import Data.Function (on)
|
||
|
|
import Data.Char (digitToInt)
|
||
|
|
|
||
|
|
column :: [String] -> Int -> String
|
||
|
|
column str i = map (!! i) str
|
||
|
|
|
||
|
|
mostCommon :: String -> Char
|
||
|
|
mostCommon str = head . maximumBy (compare `on` length) . group $ sort str
|
||
|
|
|
||
|
|
leastCommon :: String -> Char
|
||
|
|
leastCommon str = head . minimumBy (compare `on` length) . group $ sort str
|
||
|
|
|
||
|
|
-- in: input strings, sorting method, current digit
|
||
|
|
-- out: filtered strings
|
||
|
|
filterColumns :: [String] -> (String -> Char) -> Int -> [String]
|
||
|
|
filterColumns str sort i = filter (\a -> (a !! i) == commonChar) str
|
||
|
|
where
|
||
|
|
commonChar = sort $ column str i
|
||
|
|
|
||
|
|
-- in: input strings, sorting method, current digit
|
||
|
|
-- out: final rating
|
||
|
|
rating :: [String] -> (String -> Char) -> Int -> String
|
||
|
|
rating [str] _ _ = str
|
||
|
|
rating str sort i = rating (filterColumns str sort i) sort (i+1)
|
||
|
|
|
||
|
|
|
||
|
|
binaryToDecimal :: Int -> Int
|
||
|
|
binaryToDecimal = foldl1 ((+) . (2 *)) . map digitToInt . show
|
||
|
|
|
||
|
|
main :: IO ()
|
||
|
|
main = do
|
||
|
|
input <- openFile "inputs/3.txt" ReadMode
|
||
|
|
contents <- hGetContents input
|
||
|
|
|
||
|
|
let oxygen = rating (lines contents) mostCommon 0
|
||
|
|
let co2 = rating (lines contents) leastCommon 0
|
||
|
|
|
||
|
|
let rating = product (binaryToDecimal . read <$> [oxygen, co2] :: [Int])
|
||
|
|
|
||
|
|
print rating
|
||
|
|
|
||
|
|
hClose input
|