using System;

​

namespace CombinationRecursion

{

    class Program

    {

        public static void Main()

    {

         Console.Write("Input String>");

        string inputLine = "abc";

​

        Recursion rec = new Recursion();

        rec.InputSet = rec.MakeCharArray(inputLine);

        rec.CalcPermutation(0);

​

        Console.Write("# of Permutations: " + rec.PermutationCount);

    }

}

​

class Recursion

{

    private int elementLevel = -1;

    private int numberOfElements;

    private int[] permutationValue = new int[0];

​

    private char[] inputSet;

    public char[] InputSet

    {

        get { return inputSet; }

        set { inputSet = value; }

    }

​

    private int permutationCount = 0;

    public int PermutationCount

    {

        get { return permutationCount; }

        set { permutationCount = value; }

    }

​

    public char[] MakeCharArray(string InputString)

    {

        char[] charString = InputString.ToCharArray();

        Array.Resize(ref permutationValue, charString.Length);

        numberOfElements = charString.Length;

        return charString;

    }

​

    public void CalcPermutation(int k)

    {

        elementLevel++;

        permutationValue.SetValue(elementLevel, k);

​

        if (elementLevel == numberOfElements)

        {

            OutputPermutation(permutationValue);

        }

        else

        {

            for (int i = 0; i < numberOfElements; i++)

            {

                if (permutationValue[i] == 0)

                {

                    CalcPermutation(i);

                }

            }

        }

        elementLevel--;

        permutationValue.SetValue(0, k);

    }

​

    private void OutputPermutation(int[] value)

    {

        foreach (int i in value)

        {

            Console.Write(inputSet.GetValue(i - 1));

        }

        Console.WriteLine();

        PermutationCount++;

    }

}

}

​