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module Main where
import System.Environment (getArgs)
import Data.List (sort)
import qualified Data.IntMap.Strict as M
-- Delete elements from a list until element t is encountered
deleteUntil :: Eq a => [a] -> a -> [a]
deleteUntil [] _ = []
deleteUntil (x:xs) t | x == t = xs
| otherwise = deleteUntil xs t
-- Get the number of posisble valid permutations of a list of adapters
possiblePerms :: [Int] -> M.IntMap Int
possiblePerms ss = foldl addToMap (M.fromList [(0, 1)]) (sort ss ++ [end])
where getChildren x m = [k | k <- [x-3..x-1], k `M.member` m]
end = maximum ss + 3
addToMap m x = M.insert x (sum $ map (m M.!) (getChildren x m)) m
-- Read a line-seperated file of numbers
numsFromFile :: String -> IO [Int]
numsFromFile p = do
c <- readFile p;
return $ map read $ lines c;
main :: IO ()
main = do
args <- getArgs;
xs <- numsFromFile $ head args;
print $ possiblePerms xs;
return ();
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