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How do I compute the difference of two arrays? How do I compute the intersection of two arrays?

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How do I compute the difference of two arrays? How do I compute the intersection of two arrays?

Use a hash. Here's code to do both and more. It assumes that each element is unique in a given array:

    @union = @intersection = @difference = ();
    %count = ();
    foreach $element (@array1, @array2) { $count{$element}++ }
    foreach $element (keys %count) {
        push @union, $element;
        push @{ $count{$element} > 1 ? \@intersection : \@difference }, $element;
    }

Source: Perl FAQ: Data Manipulation
Copyright: Copyright (c) 1997 Tom Christiansen and Nathan Torkington.

Next: How do I find the first array element for which a condition is true?

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