You could refine that to have an out list rather than an out hash. Every value you store in it has the value 1!

my %multiples; my @out; for (@in) { if ($multiples{$_} == 1) { push @out, $_; } $multiples{$_} = 1; } print "@out";
Now since it contains only one statement, you could write the if in suffix form. You could use ++ instead of setting the count to 1 in the unconditional statement.

That gets down to:

my %multiples; my @out; for (@in) { push @out, $_ if ($multiples{$_}++ == 1) } print "@out";
That's tight enough that you can see how merlyn's form works. Just use the built-in looping mechanism of grep instead of your own foreach loop/push. It's the same thing.

He used pre-increment == 2, which you'll note is the same thing as post-increment == 1. The latter is more directly equivilent to what you had originally, but the pre-increment is arguably more efficient (though I don't know if measurably faster in Perl).


In reply to Re: Get All Duplicated Elements in an Array (Once, without shifting) by John M. Dlugosz
in thread Get All Duplicated Elements in an Array (Once, without shifting) by George_Sherston

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