comparing values between two arrays

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks - I have two arrays

 

@numbers = ('25', '12', '32','56','45','21','65');
@needed = ('25','32','45','65');
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I want to be able to iterate through @numbers, comparing each value to @needed. When there is a match, I want to get the match and all the values until the next match.

e.g.    get 25 12 32   and   45 21 65
[download]

Thankyou monks, I appreciate your help. x


 for (my $i=0; $i<@numbers; $i++)      {

   # psudocode # 

   # if $numbers[$i] matches a value in @needed;  
   # push @found, all the numbers until the next match

           for (my $k = 0; $k < @needed; $k++)   {


                 if ($numbers[$i] ==  $needed[$k])   {

                       push @found, $numbers[$i];  

    # not sure how to carry on until the next match! 
                 }

          }

   }


}
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•Re: comparing values between two arrays by merlyn (Sage) on May 20, 2003 at 10:08 UTC
So, all these years, you've been wondering what the three-dot version of the flip-flop (`..`) operator was for? Well, here it is! `my @numbers = ('25', '12', '32','56','45','21','65'); my @needed = ('25','32','45','65'); my %needed_hash = map { $_ => 1 } @needed; my @result = grep { $needed_hash{$_} ... $needed_hash{$_} } @numbers; print "@result\n";` [download] The grep test starts being true when the item is found in the hash, and also stops being true with the same test. But it won't test the stop condition on the same round as the start condition! That's why the three dots. With only two dots, it would have found the stop condition on the same item. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re: comparing values between two arrays by broquaint (Abbot) on May 20, 2003 at 10:15 UTC
Not as groovy as merlyn's post, but I'd already put this together so here it is anyway `my @numbers = ('25', '12', '32','56','45','21','65'); my @needed = ('25','32','45','65'); my @flipflop = map [$needed[$_], $needed[$_ + 1]], grep { $_ % 2 == 0 } 0 .. $#needed; for(@numbers) { print "$_ " and next if /\A$flipflop[0]->[0]\z/ .. /\A$flipflop[0]->[1]\z/; shift @flipflop and print "\n"; } __output__ 25 12 32 45 21 65` [download] See. `map`, `grep` and `perlop` for more info. HTH `_________ broquaint`	[reply] [d/l]
Re: comparing values between two arrays by dbush (Deacon) on May 20, 2003 at 10:24 UTC
merlyn and broquaint beat me to it with much better solutions, but here is my effort for what its worth. Regards, Dom. use strict; use warnings; use Data::Dumper; my @numbers = ('25', '12', '32','56','45','21','65'); my @needed = ('25','32','45','65'); my ($iNeeded, %hashNeeded, $iNumber, @result); my $bWithinMatch = 0; foreach $iNeeded (@needed) { $hashNeeded{$iNeeded} = 1 } foreach $iNumber (@numbers) { #Are we within a match? if ($bWithinMatch) {push @result, $iNumber} #Is this a needed number? if (defined $hashNeeded{$iNumber}) { #Change state $bWithinMatch = not $bWithinMatch; #If this is the start of a match, store the result if ($bWithinMatch) {push @result, $iNumber} } } print Dumper(\@result); [download] Update: Missed out the final line that dumps the result.	[reply] [d/l]
Re: comparing values between two arrays by OM_Zen (Scribe) on May 20, 2003 at 16:51 UTC
Hi , `<BR><BR> my @numbers = ('25', '12', '32','56','45','21','65'); my @needed =('25','32','45','65'); my %hashofscalars = map{ $_ ,1}@needed; my $scalar; my @res_scalars; foreach ( @numbers) { if (exists $hashofscalars{$_}){ $scalar++;push(@res_scalars ,$_); }elsif($scalar%2 != 0){ push(@res_scalars,$_) } }; print "[@res_scalars]\n"; __END__ [25 12 32 45 21 65]` [download] ~	[reply] [d/l]