#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int GLS();
int GLA();
int BBP();
int RAM();
int factorial(int number);

int main(int argc, char *argv[])
{	
  int method;
  int i;
  i = 0;
  while(i==0)
  {
  printf("Select a method to calculate pi.\n 1 - Gregory-Leibniz Series\n 2 - Gauss-Legendre Algorithm\n 3 - 
Bailey-Borwein-Plouffe Formula\n 4 - Ramanujan Series\n");
  printf("Please type in a number: 1,2,3,4\n");
  scanf("%d", &method);
  switch(method)
  {
                case 1: GLS();
                           break;
                case 2: GLA();
                           break;
                case 3: BBP();
                           break;
                case 4: RAM();
                           break;
                default:   printf("Selection not valid.\n");
                           break;  
  }
  printf("\n\nWould you like to try again? Y/N ? \n");
  scanf("%s", &method);
  switch(method)
  {
                case 'Y': printf("\n\n");
                          break;
                case 'y': printf("\n\n");
                          break;
                case 'N': 
                     {
                         i=1;
                     break;
                     }
               case 'n': 
                    {
                         i=1;
                     break;   
                     }  
               default: printf("\nSelection not valid.\n\n");
                        break;
  }
}
                     
  system("pause");
  return 0;
}

int GLS()
{
 double pi;
 pi = 0;
 int n;
 int terms;
 int digits;
 printf("Select the number of terms in the series.\n");
 scanf("%d", &terms);
 printf("Select the number of digits to display. \n");
 scanf("%d", &digits);
 for(n = 0; n < terms; n++)
 {
       pi = pi + 4*pow(-1,n)/(2*n+1);
 }
 printf("\n%1.*f\t\n", digits, pi);
 return 0;
}

int GLA()
{
 double a1,a2;
 double b1,b2;
 double t1,t2;
 double p1,p2;
 double pi;
 int n;
 int terms;
 int digits;
 printf("Select the number of iterations of the algorithm.\n");
 scanf("%d", &terms);
 printf("Select the number of digits to display. \n");
 scanf("%d", &digits);
 a1 = 1;
 b1 = 1/sqrt(2);
 t1 = .25;
 p1 = 1;
 for(n = 1; n < terms + 1; n++)
 {
       a2 = .5*(a1+b1);
       b2 = sqrt(a1*b1);
       t2 = t1 - p1*pow(a1-a2,2);
       p2 = 2*p1;
       a1 = a2;
       b1 = b2;
       t1 = t2;
       p1 = p2;
 }
 pi = pow(a1+b1,2)/(4*t1);
 printf("\n%1.*f\t\n", digits, pi);    
 return 0;
}
 
int BBP()
{
 int k;
 double pi;
 int terms;
 int digits;
 pi = 0;
 printf("Select the number of terms in the series.\n");
 scanf("%d", &terms);
 printf("Select the number of digits to display. \n");
 scanf("%d", &digits);
 for(k=0;k < terms ;k++)
 {
  pi = pi + pow(.0625,k)*(120*pow(k,2)+151*k+47)/(512*pow(k,4)+1024*pow(k,3)+712*pow(k,2)+194*k+15);
 }
 printf("\n%1.*f\t\n", digits, pi);    
 return 0;
}

int RAM()
{
 double pi;
 int k;
 double invpi;
 int terms;
 int digits;
 printf("Select the number of terms in the series.\n");
 scanf("%d", &terms);
 printf("Select the number of digits to display. \n");
 scanf("%d", &digits);
 for(k=0;k<terms;k++)
 {
 invpi = invpi + 2*sqrt(2)*factorial(4*k)*(1103+26390*k)/(9801*pow(factorial(k),4)*pow(396,4*k));
 }
 pi = 1/invpi;
 printf("\n%1.*f\t\n", digits, pi);    
 return 0;
}

int factorial(int number) {
	int temp;

	if(number <= 1) return 1;

	temp = number * factorial(number - 1);
	return temp;
}