using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        int[] a = {1, 3, 4, 6, 7, 12};

        foreach (var b in a.QuickPerm())

        {

            var c = b.ToArray();

            decimal x = (decimal)(c[0]) / (decimal)(c[1]);

            decimal y = (decimal)(c[2]) / (decimal)(c[3]);

            decimal z = (decimal)(c[4]) / (decimal)(c[5]);

            if (Math.Round(x, 2) + Math.Round(y, 2) == Math.Round(z, 2))

            {

                Console.WriteLine("{0} {1} {2} {3}", x, y, z, String.Join(", ", b));

            }

        }

​

        Console.WriteLine("Hello World");

    }

}

​

public static class Extensions

{

    public static IEnumerable<IEnumerable<T>> QuickPerm<T>(this IEnumerable<T> set)

    {

        int N = set.Count();

        int[] a = new int[N];

        int[] p = new int[N];

        var yieldRet = new T[N];

        List<T> list = new List<T>(set);

        int i, j, tmp; // Upper Index i; Lower Index j

        for (i = 0; i < N; i++)

        {

            // initialize arrays; a[N] can be any type

            a[i] = i + 1; // a[i] value is not revealed and can be arbitrary

            p[i] = 0; // p[i] == i controls iteration and index boundaries for i

        }

​

        yield return list;

        //display(a, 0, 0);   // remove comment to display array a[]

        i = 1; // setup first swap points to be 1 and 0 respectively (i & j)

        while (i < N)

        {

            if (p[i] < i)

            {

                j = i % 2 * p[i]; // IF i is odd then j = p[i] otherwise j = 0

                tmp = a[j]; // swap(a[j], a[i])

                a[j] = a[i];

                a[i] = tmp;

                //MAIN!

                for (int x = 0; x < N; x++)

                {

                    yieldRet[x] = list[a[x] - 1];

                }

​

                yield return yieldRet;

                //display(a, j, i); // remove comment to display target array a[]

                // MAIN!

                p[i]++; // increase index "weight" for i by one

                i = 1; // reset index i to 1 (assumed)

            }

            else

            {

                // otherwise p[i] == i

                p[i] = 0; // reset p[i] to zero

                i++; // set new index value for i (increase by one)

            } // if (p[i] < i)

        } // while(i < N)

    }

}