started two problems

1 files changed, 56 insertions, 0 deletions

diff --git a/08.01.hs b/08.01.hs
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+
+import System.Random
+import Control.Monad.State
+import Data.Maybe
+import Data.Tuple
+import Data.Sequence as Seq
+import Data.Foldable
+
+-- | Take a random element from a list, removing it from the list.
+randomChoice :: RandomGen g => State (Seq a, g) (Maybe a)
+randomChoice = get >>= (\(xs, g) -> if (Seq.null xs) then (return Nothing) else (let
+    (r, g2) = randomR (0, Seq.length xs - 1) g
+    in (put (deleteAt r xs, g2) >> (return (Just $ index xs r))
+  )))
+
+-- | Returns a list of randomly chosen values with no repeats.
+randomChoices :: RandomGen g => Int -> State (Seq a, g) (Seq a)
+randomChoices n = state (\si -> 
+    let (maybeVals, sf) = runState (sequence $ Prelude.replicate n randomChoice) si
+    in  (fromList $ catMaybes maybeVals, sf)
+  )
+
+data Bacterium = Red | Green deriving Show
+type Bacteria = Seq Bacterium
+
+reproduce :: Bacteria -> Bacteria
+reproduce b = b <> b
+
+eat :: RandomGen g => (Bacteria, g) -> (Bacteria, g)
+eat (b, g) = snd $ runState (randomChoices $ Seq.length b `quot` 2) (b, g)
+
+hour :: RandomGen g => (Bacteria, g) -> (Bacteria, g)
+hour (b, g) = eat (reproduce b, g)
+
+initialize :: Int -> Bacteria
+initialize n = (Seq.replicate (n `quot` 2) Red) <> (Seq.replicate (n `quot` 2) Green)
+
+isRed :: Bacterium -> Bool
+isRed Red   = True
+isRed Green = False
+
+nRed :: Bacteria -> Int
+nRed b = Seq.length $ Seq.filter isRed b
+
+isDone :: Bacteria -> Bool
+isDone b | nRed b == 0            = True
+         | nRed b == Seq.length b = True
+         | otherwise              = False
+
+run :: RandomGen g => Int -> g -> ([Bacteria], g)
+run n g = (fst <$> steps, snd $ last steps)
+          where steps = takeWhile (not . isDone . fst) $ iterate hour (initialize n, g)
+
+lifetime :: [Bacteria] -> Int
+lifetime b = Data.Foldable.length b
+