一段用来求组合数的递归代码

很久以前用来枚举组合数的，当时应该是C(4，11)。

class Program
    {
        static void Main(string[] args)
        {
            int sum = 0;
            int[] vs  = new int[4];
            int[] vars = new int[11]{1,2,3,4,5,6,7,8,9,10,11};
            G(0, 0, 4, ref vars, ref vs, ref sum);
            Console.WriteLine(sum);
        }
        static void G(int startIndex, int count, int n, ref int[] vars, ref  int[] vs, ref int sum)
        {
            if (count == n)
            {
                sum++;
                Console.WriteLine("{0}-{1}-{2}-{3}", vs[0], vs[1], vs[2], vs[3]);
            }
            else
            {
                if ((startIndex < vars.Length) && ((vars.Length - startIndex) >= (n - count)))
                {
                    vs[count] = vars[startIndex];
                    count++;
                    G(startIndex + 1, count, n, ref vars, ref vs, ref sum);
                    count--;
                    G(startIndex + 1, count, n, ref vars, ref vs, ref sum);
                }
            } 
        }
    }