C# 求列表 n个元素的 组合

        /// <summary>
        /// 求数组中n个元素的组合
        /// </summary>
        public static List<T[]> GetCombination<T>(T[] t, int n)
        {
            if (t.Length < n)
            {
                return new List<T[]>(){t};
            }
            int[] temp = new int[n];
            List<T[]> list = new List<T[]>();
            GetCombination(ref list, t, t.Length, n, temp, n);
            return list;
        }
        /// <summary>
        /// 递归算法求数组的组合(私有成员)
        /// </summary>
        private static void GetCombination<T>(ref List<T[]> list, T[] source, int totalCount, int requiredCount, int[] indexList, int M)
        {
            for (int i = totalCount; i >= requiredCount; i--)
            {
                indexList[requiredCount - 1] = i - 1;
                if (requiredCount > 1)
                {
                    GetCombination(ref list, source, i - 1, requiredCount - 1, indexList, M);
                }
                else
                {
                    if (list == null)
                    {
                        list = new List<T[]>();
                    }
                    T[] temp = new T[M];
                    for (int j = 0; j < indexList.Length; j++)
                    {
                        temp[j] = source[indexList[j]];
                    }
                    list.Add(temp);
                }
            }
        }