# Java solution to Project Euler 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:
01: 1
03: 1,3
06: 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?

Running time: 1325ms (1.3 sec)

Assessment: There’s probably a better/faster way to do this.

## 3 thoughts on “Java solution to Project Euler Problem 12”

1. Mickcao886 says:

This program has a problem: The number of factors of the program computed is wrong when “size” can be squared.

2. Ankit says:

Will you please care to explain? How did you come up to factor=factor+2;

3. aa says:

thanks .and
int factors = 0;
if(f==1) return 1; //you need to add it
for (int i = 1; i <= Math.sqrt(f); i++)
{
if (f % i == 0)
factors += 2;
}

return factors;