C program to find ncr and npr

C program to find nCr and nPr: This code calculate nCr which is n!/(r!*(n-r)!) and nPr = n!/(n-r)!

C program to find nCr using function

#include <stdio.h>
 
long factorial(int);
long find_ncr(int, int);
long find_npr(int, int);
 
int main()
{
   int n, r;
   long ncr, npr;
 
   printf("Enter the value of n and r\n");
   scanf("%d%d",&n,&r);
 
   ncr = find_ncr(n, r);
   npr = find_npr(n, r);
 
   printf("%dC%d = %ld\n", n, r, ncr);
   printf("%dP%d = %ld\n", n, r, npr);
 
   return 0;
}
 
long find_ncr(int n, int r) {
   long result;
 
   result = factorial(n)/(factorial(r)*factorial(n-r));
 
   return result;
}
 
long find_npr(int n, int r) {
   long result;
 
   result = factorial(n)/factorial(n-r);
 
   return result;
} 
 
long factorial(int n) {
   int c;
   long result = 1;
 
   for (c = 1; c <= n; c++)
      result = result*c;
 
   return result;
}

Output of program:

Another way to calculate nPr and nCr using functions

We use long long data type in our program to handle large numbers.

#include <stdio.h>
#define ll long long
 
void find_ncr_npr(int, int, ll*, ll*);
ll find_npr(int, int);
ll factorial(int);
 
int main() {
   int n, r;
   ll ncr, npr;
 
   printf("Input n and r\n");
   scanf("%d%d", &n, &r);
 
   find_ncr_npr(n, r, &npr, &ncr);
 
   printf("%dC%d = %lld\n", n, r, ncr);
   printf("%dP%d = %lld\n", n, r, npr);
 
   return 0;
}
 
void find_ncr_npr(int n, int r, ll *npr, ll *ncr) {
   *npr = find_npr(n, r);
   *ncr = *npr/factorial(r);
}
 
ll find_npr(int n, int r) {
   ll result = 1;
   int c = 1;
 
   while (c <= r) {
      result = result * (n - r + c);
      c++;
   }
 
   return result;
}
 
ll factorial(int n) {
   int c;
   ll result = 1;
 
   for (c = 1; c <= n; c++)
      result = result*c;
 
   return result;
}