18 lines
579 B
Haskell
18 lines
579 B
Haskell
import Data.List (sort, subsequences)
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isPrime :: Integer -> Bool
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isPrime n
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| n < 2 = False
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| n == 2 = True
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| otherwise = 0 == length [i | i <- [2..floor(sqrt (fromIntegral n))], n `mod` i == 0]
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isDescending :: [Integer] -> Bool
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isDescending [] = True
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isDescending [x] = True
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isDescending (x:xs) = (if x <= (head xs) then False else isDescending xs)
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getInt :: [Integer] -> Integer
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getInt = foldl (\acc x -> acc * 10 + x) 0
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descendingInts = sort [getInt xs | xs <- subsequences([9,8..1]), 0 < length xs, isDescending xs]
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main = print [n | n <- descendingInts, isPrime n]
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