16 lines
519 B
Haskell
16 lines
519 B
Haskell
-- We shall say that an n-digit number is pandigital if it makes use of all the
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-- digits 1 to n exactly once. For example, 2143 is a 4-digit pandigital and is
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-- also prime.
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--
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-- What is the largest n-digit pandigital prime that exists?
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import Euler
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pandigitals = map fromDigits $ go 9
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where go 0 = []; go n = reverse (sort (permutations [1..n])) ++ go (n-1)
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isPrime n = not $ any (\p -> n `mod` p == 0) $
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takeWhile (<= floor (sqrt (fromIntegral n))) primes
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main = print $ head $ filter isPrime pandigitals
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