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Discussion on: Daily Challenge #159 - Isogram

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Craig McIlwrath •

Haskell

import Data.Char (toLower)

noDuplicates :: (Eq a) => [a] -> Bool
noDuplicates [] = True
noDuplicates (x:xs) = not (x `elem` xs) && noDuplicates xs

isIsogram :: String -> Bool
isIsogram = noDuplicates . map toLower

I think the complexity of this method is O(n2), but it shouldn't matter too much since the since && can exit early, so the maximum number of iterations can only be 26 (by the pigeonhole principle).