euler_12.pl

#!/usr/bin/perl
use strict;
use warnings;
use Carp;
use Getopt::Long;
use Data::Dumper;
use bignum;

#PROBLEM 12
#~ The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:
#~ 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
#~ 
#~ Let us list the factors of the first seven triangle numbers:
#~ 
 #~ 1: 1
 #~ 3: 1,3
 #~ 6: 1,2,3,6
#~ 10: 1,2,5,10
#~ 15: 1,3,5,15
#~ 21: 1,3,7,21
#~ 28: 1,2,4,7,14,28
#~ We can see that 28 is the first triangle number to have over five divisors.
#~ 
#~ What is the value of the first triangle number to have over five hundred divisors?

my ( $ceiling, $help );

GetOptions(
    'c|ceiling=i'               => \$ceiling,
    'h|help'                    => \$help,
);

( $ceiling && !$help ) or die <<USAGE;
Usage: $0   
  -c|--ceiling				   <number of divisors>
  -h|--help                    <this message>
USAGE

my $notfound = 1;
my $pointer = 1;
my $triangle = 0;
while ( $notfound ) {
	$triangle += $pointer;
	$pointer++;
	my @products = getproducts( $triangle );
	my $numprod = scalar @products;
	$notfound = 0 if $numprod > $ceiling;
	#print "$triangle  ",join(',', @products), " -> [$numprod]\n";
}
print "$triangle\n";
	
sub getproducts 
{
	my ($num) = @_;
	my %rethash;
	for (my $i = 1; $i < (sqrt($num) + 1); $i++) {
		if ($num % $i == 0) {
			my $j = $num / $i;
			$rethash{$i} = 1;
			$rethash{$j} = 1;
		}
	}
	my @retarray = sort { $a <=> $b } keys %rethash;
	return @retarray;
}