Combination means way of selecting a things or particular item from the group or sets.
nCr=n!/r!(n-r)!.
Permutations means possible way of rearranging in the group or set in the particular order.
C Program
#include <stdio.h>
#include <conio.h>
main() {
int n , r, ncr( int , int);
long npr( int , int);
long double fact( int);
printf(" Enter value of n & r \n");
scanf("%d %d",&n , &r);
if( n>= r) {
printf( " %dC%d is %d\n", n,r,ncr( n , r));
printf(" %dP%d is %ld", n,r,npr( n, r));
} else {
printf("WRONG INPUT?? enter the correct input");
}
}
long double fact( int p) {
long double facts = 1;
int i;
for ( i = 1; i<= p; i++)
facts = facts * i;
return( facts);
}
int ncr ( int n, int r) {
return( fact( n) / (fact( r) * fact(n- r) ) ) ;
}
long npr( int n , int r) {
return( fact( n) / fact( n- r));
}