#include<stdio.h>//for permutation and combination
float permutation(int,int);//return type is float 
float combination(int,int);//as its return type is float ie decimal
int factorial(int);//factorial function

int main()// the main function
{
printf("In Permutation & Combination   *n>r>0*");
int n,r,choice,loop=1;// defining variable n,r and choice
float call;
while(loop)
	{
	printf("\n \t \t \t Enter 1:Permutation 2:Combination 3:Exit \n");
	scanf("%d",&choice);//asking from user which operation to perform
	if(choice==1)
		{
		printf("\n \t\t\t\t Permutation ");//displaying user which operation he chose
		printf("\n Enter n: ");//asking n from user
		scanf("%d",&n);
		printf(" Enter r: ");//R FROM USER 
		scanf("%d",&r);
		call=permutation(n,r);// CALLING FUNCTION
		printf("\n \t\t\t\t P(%d,%d) =  %f",n,r,call);
		}
	if(choice==2)
		{
		printf(" \n \t\t\t\t Combination ");
		printf("\n Enter n: ");//asking n from user
		scanf("%d",&n);
		printf(" Enter r: ");//R FROM USER
		scanf("%d",&r);
		call=combination(n,r);// FUNCTIOM CALLING 
		printf("\n \t\t\t\t C(%d,%d) = %f",n,r,call);
		}
	if(choice==3)	
		{
printf("\n \t\t\t\t   \b\b Thanks For Using This Program  :-)");
		break;
		}
	}
}
					// FUNCTION BODY
float permutation(int n,int r)
	{
	int numerator,denominator;//defining two variable numerator and denominator:wq
	numerator=factorial(n);// calculating the numerator 
	denominator=factorial(n-r);//calling function factorial for deno. ie (n-r)!
	return numerator/denominator;
	}

float combination(int n,int r)// FUNCTION BODY
	{ 
	int numerator,denominator;
	numerator=factorial(n);
	denominator=factorial(n-r)*factorial(r);
	return numerator/denominator;
	}

int factorial(int n)//function body
	{
	int result=1;// variable result
	while(n>0)//loop till n>0
		{
		result= result*n;
		n=n-1;//decreasing value of n
		}
	return result;
	}