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Re: All componens different

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112015] Re: All componens different
  • From: Patrick Scheibe <pscheibe at trm.uni-leipzig.de>
  • Date: Tue, 24 Aug 2010 06:15:41 -0400 (EDT)

Hi,

faster and shorter is

d2[v_] := Length[Union[v]] === Length[v]

Try something like

data = RandomSample[Range[10000], 10000];
d1[v_] := ! 
  Or @@ Flatten[
    Table[v[[i]] == v[[k]], {i, 1, Length[v]}, {k, i + 1, Length[v]}]];
d2[v_] := Length[Union[v]] === Length[v];
AbsoluteTiming[#[data]] & /@ {d1, d2}

gives here

{{51.339028, True}, {0.001555, True}}

Cheers
Patrick


On Mon, 2010-08-23 at 02:51 -0400, Dr. Wolfgang Hintze wrote:
> Given a list v of natural numbers I'm looking for a function d[v_] that 
> returns True if all components are different and False otherwise.
> 
> One solution is
> 
> d1[v_] := ! Or @@ Flatten[Table[v[[i]] == v[[k]], {i, 1, Length[v]}, 
> {k, i + 1, Length[v]}]]
> 
> Can you find more efficient (and elegant) solutions?
> 
> Regards,
> Wolfgang 
> 
> 



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