euler012.cpp

#include <iostream>
#include <set>
#include <math.h>

int n_divisors(int n) {
    int l = sqrt(n);
    std::set<int> f;
    f.insert(n);
    for (int i = 1; i <= l; i++)
        if (n % i == 0) {
            f.insert(i);
            f.insert(n / i);
        }

    return f.size();
}

int main() {
    int triangular = 0;
    for (int i = 1;; i++) {
        triangular += i;
        if (n_divisors(triangular) > 500) {
            std::cout << triangular << std::endl;
            return 0;
        }
    }
    return 0;
}

euler012.pl

#!/usr/bin/env perl
use 5.018;
use strict;
use warnings;

sub divisors {
    my ($n) = @_;
    my %f = ($n => 1);
    for my $i (1 .. int(sqrt($n))) {
        unless ($n % $i) {
            $f{$i}++;
            $f{int($n / $i)}++;
        }
    }
    return [keys %f];
}

my $triangular = 0;
for (my $i = 1; ; $i++) {
    $triangular += $i;
    my @divisors = @{ divisors($triangular) };
    if ($#divisors >= 500) {
        say $triangular;
        last;
    }
}

euler012.py

import math

def divisors(n):
    f = set([n])
    for i in xrange(1, int(math.sqrt(n)) + 1):
        if (n % i == 0):
            f.add(i)
            f.add(int(n / i))
    return f

triangular = 0
i = 1
while True:
    triangular += i
    if len(divisors(triangular)) > 500:
        print triangular
        break
    i += 1