In this article, we will write a C program to calculate and print the value of nPr. The formula is: nPr = n! / (n - r)!, here ! represents factorial. For example 6P2 = 6! / (6-2)! => 720 / 24 = 30.
C Program to print the value of nPr based on user input
In this program, we have defined two functions. The factorial() function is to calculate the factorial, which is required in the nPr formula. The second function nPr() is to calculate the value of nPr, this uses factorial() function.
#include <stdio.h>
/* This function calculates the factorial
* of the passed number n and returns it
*/
unsigned long long factorial(int n) {
unsigned long long fact = 1;
// Loop to calculate the factorial of n
for (int i = 1; i <= n; ++i) {
fact *= i;
}
return fact;
}
// Function to calculate nPr
unsigned long long nPr(int n, int r) {
// If r is greater than n, nPr is 0
if (r > n) return 0;
// Calculate nPr using the formula: nPr = n! / (n-r)!
return factorial(n) / factorial(n - r);
}
int main() {
int n, r;
// Prompt user to enter the value of n and r
printf("Enter value of n: ");
scanf("%d", &n); //store entered value in n
printf("Enter value of r: ");
scanf("%d", &r); //store entered value in r
// Calculate nPr
unsigned long long result = nPr(n, r);
// Print the value of nPr
printf("%dP%d = %llu\n", n, r, result);
return 0;
}
Output:
Output 1: when value of n is greater than r
Enter value of n: 5
Enter value of r: 2
5P2 = 20
Output 2: when value of r is 0
Enter value of n: 10
Enter value of r: 0
10P0 = 1
Output 3: when value of r is greater than n
Enter value of n: 4
Enter value of r: 5
4P5 = 0
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