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@mhitza
Last active December 11, 2022 08:38
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Day 11 advent of code 2022
{-# LANGUAGE BlockArguments, BangPatterns, LambdaCase, NoMonomorphismRestriction #-}
import Control.Monad.State.Strict
import Data.List
import Data.Bifunctor
import Data.Maybe
forEach xs st f = snd $ foldM (\st x -> runState (f x) st) st xs
alterF = modify . first
alterS = modify . second
getF = gets fst
data Monkey = Monkey { inspections :: Int
, items :: [Int]
, operation :: (String, String, String)
, divisionNumber :: Int
, onTrue :: Int
, onFalse ::Int
} deriving (Show)
mkPartialMonkey = Monkey 0 undefined undefined undefined undefined undefined
takeBy2 [] = []
takeBy2 ((a:b:_):xs) = read @Int [a,b] : takeBy2 xs
makeMonkeys input = reverse . snd $ forEach input (undefined,[]) $ \case
["Monkey",_] -> alterF $ const mkPartialMonkey
("Starting":_:items') -> alterF (\m -> m { items = takeBy2 items' })
["Operation:",_,_,x,op,y] -> alterF (\m -> m { operation = (x,op,y) })
["Test:",_,_,num] -> alterF (\m -> m { divisionNumber = read @Int num })
["If","true:",_,_,_,index] -> alterF (\m -> m { onTrue = read @Int index })
["If","false:",_,_,_,index] -> alterF (\m -> m { onFalse = read @Int index })
_ -> getF >>= \monkey -> alterS (monkey :)
apply (x,op,y) item = case op of
"*" -> (voi x item) * (voi y item)
"+" -> (voi x item) + (voi y item)
where voi "old" = id
voi int = const (read @Int int)
throwToMonkey n v = modify $ map appender
where appender (i,m) | i == n = (i, m { items = (items m) ++ [v] })
| otherwise = (i, m)
modifyAt n f = modify $ map (mapAt n f)
where mapAt n f (i,v) | n == i = (i,f v)
| otherwise = (i,v)
solve monkeys = result $ forEach [1..20] monkeys \_ -> gets head >>= compute
where
result = product . take 2 . reverse . sort . map (inspections . snd)
next index f =
do monkeys <- get
let found = lookup (index + 1) monkeys
if isJust found then f (index + 1, fromJust found)
else pure ()
compute (index, monkey)
| null (items monkey) = next index compute
| otherwise = do
let (item:items') = items monkey
let value = apply (operation monkey) item `div` 3
if value `mod` divisionNumber monkey == 0
then throwToMonkey (onTrue monkey + 1) value
else throwToMonkey (onFalse monkey + 1) value
let monkey' = monkey { items = items', inspections = inspections monkey + 1 }
modifyAt index (const monkey')
compute (index,monkey')
main = do
input <- ((++ [[""]]) . map words . lines) <$> readFile "/tmp/input.txt"
print $ solve (zipWith (,) [1..] (makeMonkeys input))
pure ()
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