# C program to find nCr and nPr

C program to find nCr and nPr, remember, nCr = n!/(r!*(n-r)!) and nPr = n!/(n-r)!.

## C program to find nPr and nCr using a 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;
}

Download NCR and NPR program.

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;
}