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module Main (main) where
import Control.Monad (when)
import Data.List (foldl')
import System.Exit (die)
exampleExpectedOutput = 127
parseInput :: String -> IO [Int]
parseInput filename = do
input <- readFile filename
return $ map read $ lines input
validate :: [Int] -> Int -> Bool
validate list n = processInput list
where
processInput :: [Int] -> Bool
processInput (_:[]) = False
processInput (x:xs) = (foldl' (\acc i -> acc || (x + i == n && x /= i)) False xs) || processInput xs
compute :: Int -> [Int] -> Int
compute len list
| validate (take len list) (list !! len) = compute len $ tail list
| otherwise = list !! len
main :: IO ()
main = do
example <- parseInput "example"
let exampleOutput = compute 5 example
when (exampleOutput /= exampleExpectedOutput) (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
input <- parseInput "input"
print $ compute 25 input
|
