Narcissistic decimal number: Difference between revisions
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(→Haskell - Reduced search: (used unfoldr for digitList)) |
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In this way we can find the 25th narcissistic number after '''(sum $ (length . digitGroups) <$> [1..7]) == 19447''' tests – an improvement on the exhaustive trawl through '''9926315''' integers. |
In this way we can find the 25th narcissistic number after '''(sum $ (length . digitGroups) <$> [1..7]) == 19447''' tests – an improvement on the exhaustive trawl through '''9926315''' integers. |
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<lang haskell>import Data.List (sort) |
<lang haskell>import Data.List (sort, unfoldr) |
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narcissiOfLength :: Int -> [Int] |
narcissiOfLength :: Int -> [Int] |
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digitList :: Int -> [Int] |
digitList :: Int -> [Int] |
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digitList |
digitList = |
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unfoldr |
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digitList n = rem n 10 : digitList (quot n 10) |
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(\x -> |
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if x > 0 |
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then let (q, r) = quotRem x 10 |
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in Just (r, q) |
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else Nothing) |
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digitGroups :: Int -> [[Int]] |
digitGroups :: Int -> [[Int]] |
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