Permutations, nPr can also be represented as P(n,r) is a mathematical formula to find the number of permutations. The formula of P(n, r) is n! / (n – r)!.
The number of permutations on a set of n elements is given by n! where “!” represents factorial.
Input:n=5;r=4; Output:120
Explanation
P(5, 4) = 5! / (5-4)! => 120 / 1 = 120 5!=1*2*3*4*5*=120
Example
#include<iostream>
using namespace std;
long int fact(int x) {
int i, f=1;
for(i=2; i<=x; i++) {
f=f*i;
}
return f;
}
int main() {
int n, r;
long int npr;
n=5;
r=4;
npr=fact(n)/fact(n-r);
printf("%d",npr);
}