To calculate the PERMUTAITON AND COMBINATION

Question - 

Given the value of n and r, you have to calculate the permutation and combination.

Example - 

Input : n = 10 , r = 5

Output : ncr = 252 , npr = 30240

Approach - 

We solve this question with the help of standard formula of permutation and combination.

i.e. 

npr = n!/(n-r)!

ncp = n!/(r!*(n-r)!)

Implementation - 

//permutation and combination

#include<iostream>

using namespace std;

int fact(int num)

{

    int fact=1;

    for(int i=1;i<=num;i++)

    fact*=i;

    return fact;

}

int main()

{

    int n,r;

    cout<<"Enter the value of n : ";cin>>n;

    cout<<"Enter the value of r : ";cin>>r;

    double ncr,npr;

    //ncr=n!/(r!*(n-r)!)

    //npr=n!/(n-r)!

    npr=fact(n)/fact(n-r);

    ncr=fact(n)/(fact(r)*fact(n-r));

cout<<"ncr = "<<ncr<<endl<<"npr = "<<npr<<endl;    

    

}

Code on compiler

Time complexity - O(n)