/* Binomial Coefficient - Write a function to find factorial of a number. Using this function,  find value of binomial co-efficient (B) where B = n! / r! * (n-r)!  where n and r are natural numbers. */

#include  <stdio.h>
#include  <conio.h>

long  fact(int  n) ;

void main()
{
    int  n, r ;
    long  f1, f2, f3, b ;
    clrscr() ;
    printf("Enter natural numbers n and r (n>r): ") ;
    scanf("%d %d", &n, &r) ;
    f1=fact(n) ;
    f2=fact(r) ;
    f3=fact(n-r) ;
    b=f1/(f2*f3) ;
    printf("Binomial Coefficient = %ld", b) ;
    getch() ;
}

long  fact(int  n)
{
    int  i;
    long  f=1 ;
    for(i=1 ; i<=n ; i++)
        f=f*i ;
    return  f ;
}


/*
Output:

Enter natural numbers n and r (n>r): 9  5
Binomial Coefficient = 126
*/