in reply to As Efficient as Possible

sub intersectPlus {
    my( $a, $b, $c, $d ) = @_;
    my %a; undef @a{ @$a };
    my %b; undef @b{ @$b };
    push @{ exists $a{ $_ } ? $d : $c }, $_ for keys %b;
    push @$d, @$c;
    return;
}

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Re^2: As Efficient as Possible
by mr_p (Scribe) on Apr 02, 2010 at 21:49 UTC

    Woooowww..This has to be fast.

    can you please explain what this statement does?

    push @{ exists $a{ $_ } ? $d : $c }, $_ for keys %b;
    and

    and how can u have Hash %a and array ref @$a?

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      Woooowww..This has to be fast.

      Don't guess. Test!

      Firstly that it does the same as yours does.

      And when you are sure it does, then time both with the same data.

      can you please explain what this statement does? push @{ exists $a{ $_ } ? $d : $c }, $_ for keys %b;

      1. It iterates over the unique values in the B array,
      2. and if that value exists in the A array, it exists in both, so it pushes it to the D (intersection) array.
      3. otherwise, it only exists in the B array, so it pushes it to the (B only) C array.
      and how can u have Hash %a and array ref @$a?

      There is no conflict. You can have $a, @a, & %a all in the same scope.

      But, rename them to whatever suites your personal preference.

      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
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        Thanks for the explanation and the function. I will test and let u know. Thanks again.
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