PROJECT EULER SOLUTION # 12

Solution to problem number 12 of Project Euler.

Question # 12

The sequence of triangle numbers is generated by adding the natural numbers. So the 7^th 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?

Solution # 12

/*********************************************************************/

#include<stdio.h>

#include<time.h>

#include<stdlib.h>

#include<conio.h>

#include<math.h>

int no_of_divisors(long);

int main()

{

                int i,counter;

                long tri_no;

               

                for(i=1;;i++)

                {

                                tri_no=(i+1)*i/2;

                                if(no_of_divisors(tri_no)>500)

                                {

                                                printf("\nAnswer = %ld\n",tri_no,i);

                                                break;

                                }

                               

                }

                printf("\nEXECUTION TIME = %f\n",clock()/(float)CLK_TCK);

                system("pause");

}

int no_of_divisors(long num)

{

                long i;

                double s;

                int counter=0;

               

                for(i=1;i<sqrt((double)num);i++)

                                if(num%i==0)

                                                counter++;

                counter*=2;

                s=sqrt((double)num);

                if(s*s==num)

                                counter++;

                return counter;

}

/*********************************************************************/