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Diffstat (limited to '2020/01/first.hs')
-rw-r--r-- | 2020/01/first.hs | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/2020/01/first.hs b/2020/01/first.hs new file mode 100644 index 0000000..5a615a9 --- /dev/null +++ b/2020/01/first.hs @@ -0,0 +1,29 @@ +module Main where + +import Control.Monad (when) +import Data.Maybe (catMaybes, fromJust) +import System.Exit (die) + +exampleExpectedOutput = 514579 + +compute2020 :: Int -> Int -> Maybe Int +compute2020 a b + | a + b == 2020 = Just (a * b) + | otherwise = Nothing + +compute :: String -> Int +compute input = head . catMaybes $ processInput inputList + where + inputList :: [Int] + inputList = map read $ lines input + processInput :: [Int] -> [Maybe Int] + processInput (_:[]) = [Nothing] + processInput (x:xs) = map (compute2020 x) xs ++ processInput xs + +main :: IO () +main = do + example <- readFile "example" + let exampleOutput = compute example + when (exampleOutput /= exampleExpectedOutput) (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput) + input <- readFile "input" + print $ compute input |