Narcissistic decimal number: Difference between revisions
→Haskell - Reduced search: (used unfoldr for digitList)
(→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.
<lang haskell>import Data.List (sort, unfoldr)
narcissiOfLength :: Int -> [Int]
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digitList :: Int -> [Int]
digitList
unfoldr
(\x ->
if x > 0
then let (q, r) = quotRem x 10
in Just (r, q)
else Nothing)
digitGroups :: Int -> [[Int]]
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