Re: [Haskell-cafe] Re: Function to detect duplicates

Am Dienstag 23 Februar 2010 13:03:45 schrieb Ertugrul Soeylemez:

Rafael Gustavo da Cunha Pereira Pinto wrote:

...

While solving a puzzle, I was posed the problem of finding if there was no duplicates on a list.

First I used:

noneRepeated=null.(filter (>1)).(map length).group.sort

But this seemed very unneficient, so I thought that I could detect the duplicates while sorting, and devised this:

import Control.Monad import Data.Maybe

noneRepeated=isNothing . (foldl merge (Just [])) . (map sort) . pairs

import Data.List

noneRepeated xs = xs == nub xs

Talk about inefficiency :) import Data.Set (Set) import qualified Data.Set as Set noneRepeated = go 0 Set.empty where go ct st (x:xs) | Set.size st < ct = False | otherwise = go (ct+1) (Set.insert x st) xs go ct st [] = ct == Set.size st

Greets Ertugrul