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module Day9A where
import System.Environment (getArgs)
potentialSum :: [Int] -> Int -> [(Int, Int)]
potentialSum xs t = filter ((== t) . uncurry (+)) [(x, y) | x <- xs, y <- xs, x /= y]
mapSumPrev :: [Int] -> Int -> [[(Int, Int)]]
mapSumPrev xs l = [potentialSum (take l $ drop (i - l) xs) v | (i, v) <- zip [25..] (drop l xs)]
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;
let unob = head $ filter (null . fst) $ zip (mapSumPrev xs 25) [25..];
let unob_n = xs !! snd unob;
putStrLn $ "No way to sum up to " ++ show unob_n;
return ();
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