C# Calculate nPr

This program calculates nPr. Here There are n! (n factorial) permutations of n symbols. A r-permutation of n symbols is a permutation of r of them. There are n!/(n – r)! different r-permutations of n symbols.

using System;

namespace Program
{
    class Program
    {
        static void Main(string[] args)
        {
            int n, r, per, fact, fact1;

            Console.WriteLine("Enter the Value of 'n' and 'r' to find the Permutation:");

            n = Convert.ToInt32(Console.ReadLine());
            r = Convert.ToInt32(Console.ReadLine());
            fact = n;

            for (int i = n - 1; i >= 1; i--)
            {
                fact = fact * i;
            }

            int number;
            number = n - r;
            fact1 = number;

            for (int i = number - 1; i >= 1; i--)
            {
                fact1 = fact1 * i;
            }

            per = fact / fact1;
            Console.WriteLine("Permutation : {0}", per);

            Console.ReadLine();
        }
    }
}

 

Output