use strict;
use warnings;
use Benchmark qw(timethese);

my $nb_elements = 2e6;
my @top3;

my @startArray;

push @startArray, ["", "", int rand (1e7)] for 1..$nb_elements;

sub discard_sort{ 
    my @masterArray = @startArray;
	my @top3 = sort {$b->[2] <=> $a->[2]} @masterArray[0..2];
	my $min_top = $top3[2][2];
	$nb_elements--;
	for my $sub_aref (@masterArray [3..$nb_elements]) {
		next if $sub_aref->[2] <= $min_top;
		@top3 =  (sort {$b->[2] <=> $a->[2]} $sub_aref, @top3)[0..2];
		$min_top = $top3[2][2];
	}
}

sub discard_manual{ 
    my @masterArray = @startArray;
	@top3 = sort {$b->[2] <=> $a->[2]} @masterArray[0..2];
	my $min_top = $top3[2][2];
	$nb_elements--;
	for my $sub_aref (@masterArray [3..$nb_elements]) {
		next if $sub_aref->[2] <= $min_top;
		if ($sub_aref->[2] > $top3[0][2]) {
			unshift @top3, $sub_aref;
			pop @top3;
		} 
		elsif ( $sub_aref->[2] > $top3[1][2]) {
			$top3[2] = $top3[1];
			$top3[1] = $sub_aref;
		} else {
			pop @top3;
			push @top3, $sub_aref;
		} 
		$min_top = $top3[2][2];
	}
}

sub sort_strategy {
	my @masterArray = @startArray;
	my @top3 = (sort {$b->[2] <=> $a->[2]} @masterArray)[0..2];
}

timethese (5, {  
	'walk once with sort' => \&discard_sort,
	'walk once manual insert' => \&discard_manual,
	'sort' => \&sort_strategy});