[Israel.pm] exists item in array

Ernst, Yehuda yernst at nds.com
Tue Oct 9 00:40:07 PDT 2007


what is the fastest way if i have 100000 items?

-----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
This e-mail is confidential, the property of NDS Ltd and intended for the addressee only.  Any dissemination, copying or distribution of this message or any attachments by anyone other than the intended recipient is strictly prohibited.  If you have received this message in error, please immediately notify the postmaster at nds.com and destroy the original message.  Messages sent to and from NDS may be monitored.  NDS cannot guarantee any message delivery method is secure or error-free.  Information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses.  We do not accept responsibility for any errors or omissions in this message and/or attachment that arise as a result of transmission.  You should carry out your own virus checks before opening any attachment.  Any views or opinions presented are solely those of the author and do not necessarily represent those of NDS.

NDS Limited Registered office: One Heathrow Boulevard, 286 Bath Road, West Drayton, Middlesex, UB7 0DQ, United Kingdom. A company registered in England and Wales  Registered no. 3080780   VAT no. GB 603 8808 40-00

To protect the environment please do not print this e-mail unless necessary.

More information about the Perl mailing list