Project Euler 12 requires counting how many divisors a number has. It only wants positive divisors, and 1 and the number itself count. So, the number 12 has six divisors: 1, 2, 3, 4, 6, and 12.
You're trying to find the first triangle number that has 500 divisors. Well, I'd like to not bother calculating triangle numbers that aren't going to have anywhere near 500 divisors so I want to know how high numbers have to get before they start approaching having 500 divisors.
I wrote this program to loop from 1 to a high number, count how many divisors each number has (and dump it to a text file), report which number had the highest number of divisors, and the number of divisors it had.
I had hoped to graph it out see it generally rise and maybe guess about where it would hit the 500 mark, but I ran it from 1 to a million and it only got to around 200.
The program would eventually get me the answer I want but once the numbers get high my CountDivisors() function starts really slowing down. Now I'm researching faster options using recursion.
This exercise is also revealing how much basic math I've lost over the years. Like the difference between divisors and factors. Divisors will divide a number with no remainder and factors will multiply into the number (which can be broken down into a set of prime numbers). Terminology, woof. I need a fifth grade math book on hand.
EDIT: I set the upper limit of numbers to get divisors from to 3 million. I started it this morning and it's still going. I'm about to head out for the afternoon so I'll leave it running. I think I'll stop it tomorrow morning if it isn't done yet. I got rid of the printf statements since they do indeed slow down the process but now I'm not sure where it's at in the loop.
No comments:
Post a Comment