C# Calculate the Value of nCr

This program calculates the Value of nCr. Here The Combination represented by nCr and each r combination can be arranged in r! different ways. Then the number of r-permutations is equal to the number of r combinations times r!.

using System;

namespace Program
{
    class Program
    {
        static void Main(string[] args)
        {
            int n, r, per, fact, fact1, fact2;

            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;
            }

            fact2 = r;

            for (int i = r - 1; i >= 1; i--)
            {
                fact2 = fact2 * i;
            }

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

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

            fact1 = fact2 * fact1;
            per = fact / fact1;

            Console.WriteLine("Combination: {0}", per);

            Console.ReadLine();
        }
    }
}

 

Output