No comments on Heap not having ever used it.

However, unless you are dynamically adding and removing items to your dataset wouldn't something like:

sub smallest_n (&\@$) {
    my ($cmp, $arrayref, $n) = @_;
    return unless $n && @$arrayref;
    $n = @$arrayref if @$arrayref < $n;
    my @results = sort $cmp @$arrayref[0..$n-1];
    local ($a, $b);
    $a = pop @results;
    for (my $i = $n; $i < @$arrayref; $i++) {
        $b = $arrayref->[$i];
        if ($cmp->() == 1) {
            @results = sort $cmp (@results, $b);
            $a = pop @results;
        };
    };
    return (@results, $a);
};

use Test::More tests => 1;
use List::Util qw(shuffle);
my @a = shuffle (1..100000);
my @b = smallest_n {$a <=> $b} @a, 5;
is_deeply [@b], [1,2,3,4,5];

[download]

be easier? The support for the heap datastructure will add a fair bit of overhead with your large dataset, so I wouldn't use one unless you need it.

Update: totally misready what blakem was proposing. D'oh.

In reply to Re: Heap sorting in perl by adrianh
in thread Heap sorting in perl by blakem

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