day6: Complete first puzzle

6/Parsing.hs

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+module Parsing (
+  splitByString
+  ) where
+
+import           Data.List (isPrefixOf)
+
+splitByString :: String -> String -> [String]
+splitByString _ "" = []
+splitByString splitter string =
+  let (chunk, rest) = spanNextSplit string
+  in
+    chunk:(splitByString splitter rest)
+    where
+      spanNextSplit :: String -> (String, String)
+      spanNextSplit [] = ([], [])
+      spanNextSplit everything@(char:rest)
+        | splitter `isPrefixOf` rest =
+          ([char], (drop ((length splitter) + 1) everything))
+        | otherwise =
+          let
+            (start, end) = spanNextSplit rest
+          in
+            (char:start, end)

6/fishexploder.hs

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+import           Parsing (splitByString)
+
+main :: IO ()
+main = do
+  input <- getContents
+  let
+    fish = parseFish input
+  (putStrLn . show . solution1) fish
+
+solution1 :: [Int] -> Int
+solution1 = length . (simulateDays 80)
+
+parseFish :: String -> [Int]
+parseFish = (map read) . (splitByString ",")
+
+simulateDays :: Int -> [Int] -> [Int]
+simulateDays days fish = foldr (\f acc -> f acc) fish (replicate days tickDay)
+
+tickDay :: [Int] -> [Int]
+tickDay [] = []
+tickDay (fish:otherFish)
+  | fish == 0 = 6:8:(tickDay otherFish)
+  | otherwise = (fish - 1):(tickDay otherFish)
+
+-- Tests
+
+testInput = "3,4,3,1,2"
+testParsed = parseFish testInput
+
+test1 = solution1 (parseFish testInput)
+
+testTick = (tickDay . tickDay) testParsed
+testSimulate = length (simulateDays 80 testParsed)

6/input.txt

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+3,1,5,4,4,4,5,3,4,4,1,4,2,3,1,3,3,2,3,2,5,1,1,4,4,3,2,4,2,4,1,5,3,3,2,2,2,5,5,1,3,4,5,1,5,5,1,1,1,4,3,2,3,3,3,4,4,4,5,5,1,3,3,5,4,5,5,5,1,1,2,4,3,4,5,4,5,2,2,3,5,2,1,2,4,3,5,1,3,1,4,4,1,3,2,3,2,4,5,2,4,1,4,3,1,3,1,5,1,3,5,4,3,1,5,3,3,5,4,2,3,4,1,2,1,1,4,4,4,3,1,1,1,1,1,4,2,5,1,1,2,1,5,3,4,1,5,4,1,3,3,1,4,4,5,3,1,1,3,3,3,1,1,5,4,2,5,1,1,5,5,1,4,2,2,5,3,1,1,3,3,5,3,3,2,4,3,2,5,2,5,4,5,4,3,2,4,3,5,1,2,2,4,3,1,5,5,1,3,1,3,2,2,4,5,4,2,3,2,3,4,1,3,4,2,5,4,4,2,2,1,4,1,5,1,5,4,3,3,3,3,3,5,2,1,5,5,3,5,2,1,1,4,2,2,5,1,4,3,3,4,4,2,3,2,1,3,1,5,2,1,5,1,3,1,4,2,4,5,1,4,5,5,3,5,1,5,4,1,3,4,1,1,4,5,5,2,1,3,3