Project Euler Problem 1

Endeavoring to be more of a producer than a consumer, ran across Project Euler which looks to be low friction but somewhat useful and interesting. Unfortunately their register/login system is broken:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/admin/domains/projecteuler.net/public_html/includes/login_preprocess.php on line 11

So I’ll keep track on my own blog I guess and see how far along I get.

Problem 1:

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

And my solution, in PHP:

$sum = 0;

for($i = 0; $i < 1000; ++$i) { if(!($i % 3) || !($i % 5)) { $sum += $i; } } echo number_format($sum); [/php] Answer: 233,168