25 lines
458 B
Haskell
25 lines
458 B
Haskell
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#!/usr/bin/env runghc
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import Data.List
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import Data.Maybe
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main :: IO ()
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main =
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do
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input <- getInput
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let answer = uncurry (*) $ fromJust $ find isSolutionPair $ pairs input
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putStrLn $ show answer
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getInput :: IO [Int]
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getInput = fmap (map read . lines) getContents
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pairs :: [a] -> [(a, a)]
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pairs [] = []
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pairs [_] = []
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pairs (x:xs) = [(x, y) | y <- xs] ++ pairs xs
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isSolutionPair :: (Int, Int) -> Bool
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isSolutionPair (a, b) = a + b == 2020
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