C program to calculate and print the value of nCr (Combination)

In the following example of C program to calculate and print the value of nCr (combination) :

Program :

#include <stdio.h>

int factorial(int n) {
    if (n == 0) {
        return 1;
    }
    else {
        return n * factorial(n-1);
    }
}

int nCr(int n, int r) {
    return factorial(n) / (factorial(r) * factorial(n-r));
}

int main() {
    int n, r;

    printf("Enter the value of n: ");
    scanf("%d", &n);

    printf("Enter the value of r: ");
    scanf("%d", &r);

    if (n < r) {
        printf("Invalid input: n should be greater than or equal to r\n");
    }
    else {
        printf("%dC%d = %d\n", n, r, nCr(n, r));
    }

    return 0;
}

Output :

Enter the value of n: 6
Enter the value of r: 5
6C5 = 6

* In this program, the factorial function is defined to calculate the factorial of a given integer. The nCr function calculates the combination of n and r using the formula n!/(r!(n-r)!).

* The main function prompts the user to enter the values of n and r, checks whether n is greater than or equal to r, and prints the result of the combination if the input is valid.