28 lines
1.3 KiB
Haskell
28 lines
1.3 KiB
Haskell
import Data.List (transpose)
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import Data.List.Split (splitOn)
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type Equation = (Int, [Int])
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concatInt :: Int -> Int -> Int
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concatInt x y = read $ show x ++ show y
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isSolvable :: Int -> Equation -> Bool
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isSolvable cur (result, []) = cur == result
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isSolvable cur (result, [x]) = cur + x == result || cur * x == result || cur `concatInt` x == result
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isSolvable cur (result, x:y:ys) = isSolvable (cur + x + y) (result, ys)
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|| isSolvable ((cur + x) * y) (result, ys)
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|| isSolvable ((cur + x) `concatInt` y) (result, ys)
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|| isSolvable (cur * x + y) (result, ys)
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|| isSolvable (cur * x * y) (result, ys)
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|| isSolvable ((cur * x) `concatInt` y) (result, ys)
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|| isSolvable ((cur `concatInt` x) + y) (result, ys)
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|| isSolvable ((cur `concatInt` x) * y) (result, ys)
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|| isSolvable ((cur `concatInt` x) `concatInt` y) (result, ys)
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main = do
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[x, y] <- transpose . map (splitOn ":") . lines <$> readFile "day7.txt"
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let results = map read x
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values = map read <$> map words y
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equations = zip results values
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print . sum . map fst $ filter (isSolvable 0) equations
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