What's the most efficient way to check for duplicates in an array of data using Perl?

Question

I need to see if there are duplicates in an array of strings, what\'s the most time-efficient way of doing it?

Answer 1

If you need the uniquified array anyway, it is fastest to use the heavily-optimized library List::MoreUtils, and then compare the result to the original:

use strict;
use warnings;
use List::MoreUtils 'uniq';

my @array = qw(1 1 2 3 fibonacci!);
my @array_uniq = uniq @array;
print ((scalar(@array) == scalar(@array_uniq)) ? "no dupes" : "dupes") . " found!\n";

Or if the list is large and you want to bail as soon as a duplicate entry is found, use a hash:

my %uniq_elements;
foreach my $element (@array)
{
    die "dupe found!" if $uniq_elements{$element}++;
}