Factorial function 

1. Definition:

The factorial of an integer "n" is the following product:
factorial = 1 x 2 x 3 x 4 x ... x n . Written as n!.

Here we have used two methods, the recursive method 
and the iterative method. The first one is more compact..


Two methods in C language:

	
#include 
#include 


// Recursive function


int factorial (int n)
{
if (n <= 1)
return 1;
else
return n * factorial (n-1);
}


//Iterative functions


//1.
int factorial1(int n)
{
	int i;
	int facto = 1;

for(i=n;i>=1;i--)
{
facto=facto*i;
}
return facto;
}

//2.

int factorial2(int n)
{
	int i;
	int facto = 1;

for(i=1; i<=n; i++)
{
facto= facto*i;
}
return facto;
}


int main()
{
int n;
printf("\n Enter an integer\n");
scanf("%d",&n);
	printf("\n The factorial of %d is %d: \n", n,factorial(n));
	printf("\n");
	printf("\n The factorial of %d is %d: \n", n,factorial1(n));
	printf("\n");
	printf("\n The factorial of %d is %d: \n", n,factorial1(n));
return 0;
}