Day 6

advent-of-code.cabal

@@ -61,10 +61,12 @@ executable aoc-05b
 executable aoc-06a
   import              : aoc-common
   main-is             : AOC-06a.hs
+  build-depends       : array
 
 executable aoc-06b
   import              : aoc-common
   main-is             : AOC-06b.hs
+  build-depends       : array
 
 executable aoc-07a
   import              : aoc-common

data/lantern-fish.txt

+3,4,1,2,1,2,5,1,2,1,5,4,3,2,5,1,5,1,2,2,2,3,4,5,2,5,1,3,3,1,3,4,1,5,3,2,2,1,3,2,5,1,1,4,1,4,5,1,3,1,1,5,3,1,1,4,2,2,5,1,5,5,1,5,4,1,5,3,5,1,1,4,1,2,2,1,1,1,4,2,1,3,1,1,4,5,1,1,1,1,1,5,1,1,4,1,1,1,1,2,1,4,2,1,2,4,1,3,1,2,3,2,4,1,1,5,1,1,1,2,5,5,1,1,4,1,2,2,3,5,1,4,5,4,1,3,1,4,1,4,3,2,4,3,2,4,5,1,4,5,2,1,1,1,1,1,3,1,5,1,3,1,1,2,1,4,1,3,1,5,2,4,2,1,1,1,2,1,1,4,1,1,1,1,1,5,4,1,3,3,5,3,2,5,5,2,1,5,2,4,4,1,5,2,3,1,5,3,4,1,5,1,5,3,1,1,1,4,4,5,1,1,1,3,1,4,5,1,2,3,1,3,2,3,1,3,5,4,3,1,3,4,3,1,2,1,1,3,1,1,3,1,1,4,1,2,1,2,5,1,1,3,5,3,3,3,1,1,1,1,1,5,3,3,1,1,3,4,1,1,4,1,1,2,4,4,1,1,3,1,3,2,2,1,2,5,3,3,1,1
\ No newline at end of file

src/AOC-06a.hs

+{-# LANGUAGE TypeApplications #-}
+  
 module Main where
 
+import Data.Array
+
+type Population = Array Int Int
+
+step :: Population -> Population
+step a = array (0,8) [(x,f x) | x <- [0..8]] where
+  f 8 = a ! 0
+  f 6 = a ! 7 + a ! 0
+  f n = a ! (n+1)
+
+makeFish :: [Int] -> Array Int Int
+makeFish = accumArray (+) 0 (0,8) . map (\x -> (x,1))
 main :: IO ()
-main = pure ()
+main = do
+  phases <- makeFish . read @[Int] . ("["++) . (++"]") <$> readFile "data/lantern-fish.txt"
+  print . sum $ iterate step phases !! 80
+

src/AOC-06b.hs

+{-# LANGUAGE TypeApplications #-}
+  
 module Main where
 
+import Data.Array
+
+type Population = Array Int Int
+
+step :: Population -> Population
+step a = array (0,8) [(x,f x) | x <- [0..8]] where
+  f 8 = a ! 0
+  f 6 = a ! 7 + a ! 0
+  f n = a ! (n+1)
+
+makeFish :: [Int] -> Array Int Int
+makeFish = accumArray (+) 0 (0,8) . map (\x -> (x,1))
 main :: IO ()
-main = pure ()
+main = do
+  phases <- makeFish . read @[Int] . ("["++) . (++"]") <$> readFile "data/lantern-fish.txt"
+  print . sum $ iterate step phases !! 256
+

test/lantern-fish.txt

+3,4,3,1,2