[Israel.pm] exists item in array

Oron Peled oron at actcom.co.il
Tue Oct 9 14:50:54 PDT 2007


On Tuesday, 9 בOctober 2007, Ernst, Yehuda wrote:
> thanks!
> 
> what is the fastest way if i have 100000 items?

Ahhhh, you meant you are going to benchmark it for us?
Please do so and let us know the results.

Thanks,

> 
> -----Original Message-----
> From: Oron Peled [mailto:oron at actcom.co.il]
> Sent: Monday, October 08, 2007 11:11 PM
> To: perl at perl.org.il
> Cc: Ernst, Yehuda
> Subject: Re: [Israel.pm] exists item in array
> 
> 
> On Monday, 8 בOctober 2007, Ernst, Yehuda wrote:
> > I want to enter items to array only if they does not exits there
> > (i need 1 item of each type) 
> > if i have     a b c d d d c
> > the array will have
> > a b c d
> 
> That was one of my favorites when I was teaching perl.
> 
> Several alternative solutions (with different conditions):
> 
>   @in = ('a', 'c', 'c', 'd', 'd', 'd', 'c');
> 
> 1. Assume sorted items (your example), preserve order:
> 
>   my $prev = 'nosuchvalue';
>   @out = grep($_ ne $prev && ((($prev) = $_),1), @in);
> 
> 2. Any order input, preserve order:
> 
>   undef %saw;
>   @out = grep(!$saw{$_}++, @in);
> 
> 3. Any order input, does not preserve order:
> 
>   undef %a;
>   @a{@in} = ();
>   @out = keys(%a);
> 
> 4. Any order input, @in contains (not very large) numbers,
>    does not preserve order:
> 
>   @a[@in] = @in;
>   @out = sort @a;
> 
> Have fun,
> 
> -- 
> Oron Peled                             Voice/Fax: +972-4-8228492
> oron at actcom.co.il                  http://www.actcom.co.il/~oron
> ICQ UIN: 16527398
> 
> "Beware of bugs in the above code;
>  I have only proved it correct, not tried it."
>                               -- Donald E. Knuth
> 
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-- 
Oron Peled                             Voice/Fax: +972-4-8228492
oron at actcom.co.il                  http://www.actcom.co.il/~oron
ICQ UIN: 16527398

Programming today is a race between software engineers striving to build
bigger and better idiot-proof programs, and the universe trying to produce
bigger and better idiots. So far, the universe is winning.
-- Rick Cook, Mission Manager, NASA Mars Pathfinder Project



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