Day 6

Day6.hs

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+module Day6 where
+import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
+import Data.Text (splitOn, unpack, pack)
+import Prelude hiding (splitAt)
+
+splitAt :: String -> String -> [String]
+splitAt delimiter str = map unpack $ splitOn (pack delimiter) $ pack str
+
+grow :: Int -> [Int]
+grow f
+    | f > 0 = [f - 1]
+    | otherwise  = [6, 8]
+
+main :: IO ()
+main = do
+    input <- openFile "inputs/6.txt" ReadMode
+    contents <- hGetContents input
+
+    let fishies = map read $ splitAt "," contents :: [Int]
+
+    print . length . (!! 80) $ iterate (concatMap grow) fishies
+
+    hClose input

Day6_1.hs

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+module Day6_1 where
+import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
+import Data.Text (splitOn, unpack, pack)
+import Prelude hiding (splitAt)
+import Data.List (group, sort)
+import Data.Map.Strict (toList, fromListWith)
+
+splitAt :: String -> String -> [String]
+splitAt delimiter str = map unpack $ splitOn (pack delimiter) $ pack str
+
+count :: [Int] -> [(Int, Int)]
+count fish = map (\x -> (head x, length x)) $ group $ sort fish
+
+grow :: (Int, Int) -> [(Int, Int)]
+grow fish
+    | fst fish > 0 = [(fst fish - 1, snd fish)]
+    | otherwise = [(6, snd fish), (8, snd fish)]
+
+sumFishes :: [(Int, Int)] -> [(Int, Int)]
+sumFishes = toList . fromListWith (+)
+
+main :: IO ()
+main = do
+    input <- openFile "inputs/6.txt" ReadMode
+    contents <- hGetContents input
+
+    let fishies = map read $ splitAt "," contents :: [Int]
+    print . sum . map snd . (!! 256) . iterate (sumFishes . concatMap grow) $ count fishies
+
+    hClose input