任意数相加算法有关问题

任意数相加算法问题
19个数，任意个数相加，要求选出等于一个定数的组合。19个数最大2万，最小500，小数点不超过2位。求大神这算法怎么弄？
由于个数不定，用排列组合数量会非常大，没什么思路。
------解决思路----------------------

private List<string> GetPlusRet(Single CosData, params string [] strDatas)

        {

            List<string> retdata = new List<string>();


            List<Single> lstSig = new List<Single>();


            //WriteCombinations<string>(strDatas, 3);


            var c = new string[] { "14", "4.3", "12", "21.7" };

            for (Int32 i = 1; i <= 4; i++)

            {

                WriteCombinations<string>(c, i, CosData);

            }

            



            return retdata;

        }


        static void WriteCombinations<T>(T[] array, int length,Single Data)

        {

            var combinations = new Combinations<T>(array, length);

            foreach (var oneCom in combinations)

            {

                var sb = new StringBuilder();

                Single ret = 0;

                foreach (T item in oneCom)

                {

                    ret += Convert.ToSingle(item.ToString());

                    sb.Append(item.ToString() + ",");

                }

                if (sb.Length > 0) sb.Remove(sb.Length - 1, 1);

                if (Data == ret)

                    Console.WriteLine(ret.ToString());

                Console.WriteLine(sb.ToString() );

            }

            Console.WriteLine(combinations.ToString());

            Console.WriteLine();

        }



        public class Combinations<T>

        {

            #region メンバ

            private IList<T> _items;

            private int _length;

            private List<IList<T>> _combinations;

            private int[] _finalIndices;

            #endregion


            #region コンストラクタ

            public Combinations(IList<T> items) : this(items, items.Count) { }

            public Combinations(IList<T> items, int select)

            {

                if (select < 0)

                    throw new ArgumentException("選択要素数は、0以上でなくてはなりません。");

                if (items.Count < select)