TriangleNumber.java

package problem12;

/*
Highly divisible triangular number
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?
*/
public class TriangleNumber {
   public static void main(String[] args) {
      int divisorCount = 0, triangleCount = 1, testTriangle = 0;
      while (divisorCount < 501) {
         divisorCount = 0;
         testTriangle = generateTriangle(triangleCount);
         for (int i = 1; i * i <= testTriangle; i++) {
            if (testTriangle % i == 0) {
               divisorCount += 2;
            }
         }
         triangleCount++;
      }
      System.out.println(testTriangle);
   }

   public static int generateTriangle(int number) {
      int sum = 0;
      for (int i = 1; i <= number; i++) {
         sum += i;
      }
      return sum;
   }
}