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(); } } }
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