private static Tuple<List<int>, int> NextPermutation(int gen, List<int> x)
        {
            int n = x.Count;
            int pos,pos1;

            if (gen == 0)
            {
                for (int i = 0; i <= n - 1;i++)
                {
                    x[i] = i;
                }

                gen = 1;
                return new Tuple<List<int>, int>(x,gen);
            }

            pos = -1;
            for (int i = n - 2; i >= 0; i--)
            {
                if (x[i] < x[i + 1])
                {
                    pos = i;
                    break;
                }
            }

            if (pos == -1)
            {
                gen = 0;
                return new Tuple<List<int>, int>(x, gen);
            }

            pos1 = pos + 1;
            for (int j = n - 1; j >=pos+1; j--)
            {
                if (x[j] > x[pos])
                {
                    pos1 = j;
                    break;
                }
            }

            int temp = x[pos];
            x[pos] = x[pos1];
            x[pos1] = temp;

            int a= pos+1;
            int b = n-1;
            while (a < b)
            {
                temp = x[a];
                x[a] = x[b];
                x[b] = temp;
                a++;
                b--;
            }
            return new Tuple<List<int>, int>(x, gen);
        }


    }