in reply to Finding Redundant values in arrays

You can count occurrences using a hash:

@test = ("camel","alpaca","penguin","alpaca","monkey","camel","camel")
+;
my %counts;
$counts{$_}++ foreach @test;
@redundant = grep { $counts{$_}>1 } keys(%counts);

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And please note that camels are never redundant <g>.

update: changed map to foreach so as to avoid the dreaded map in void context

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Re: Re: Finding Redundant values in arrays
by ChemBoy (Priest) on Jun 08, 2001 at 01:11 UTC

    or, for slightly better performance (IIRC), ditch map in void context, and use 

    $counts{$_}++ for @test;

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    or (for us antediluvian 5.004 types) 
    for (@test) {$counts{$_}++}

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    I was hoping there was a Schwartzian Transform analog for this, just for the fun of running the whole thing into one line, but I can't come up with one.

    Update:
    No sooner posted than obsolete... 

    @redundant = grep {++$counts{$_} > 1} @test;

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    Oops! 
    @redundant = grep {++$counts{$_}==2} @test;

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    and a pox on foolish monks who post without full testing...


    If God had meant us to fly, he would *never* have give us the railroads.
        --Michael Flanders

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