c# 排列组合代码类

/// <summary>
        /// 排列组件算法类
        /// </summary>
        /// <typeparam name="T"></typeparam>
        public class PermutationAndCombination<T>
        {
            /// <summary>
            /// 交换两个变量
            /// </summary>
            /// <param name="a">变量1</param>
            /// <param name="b">变量2</param>
            public static void Swap(ref T a, ref T b)
            {
                T temp = a;
                a = b;
                b = temp;
            }
            /// <summary>
            /// 递归算法求数组的组合(私有成员)
            /// </summary>
            /// <param name="list">返回的范型</param>
            /// <param name="t">所求数组</param>
            /// <param name="n">辅助变量</param>
            /// <param name="m">辅助变量</param>
            /// <param name="b">辅助数组</param>
            /// <param name="M">辅助变量M</param>
            private static void GetCombination(ref List<T[]> list, T[] t, int n, int m, int[] b, int M)
            {
                for (int i = n; i >= m; i--)
                {
                    b[m - 1] = i - 1;
                    if (m > 1)
                    {
                        GetCombination(ref list, t, i - 1, m - 1, b, M);
                    }
                    else
                    {
                        if (list == null)
                        {
                            list = new List<T[]>();
                        }
                        T[] temp = new T[M];
                        for (int j = 0; j < b.Length; j++)
                        {
                            temp[j] = t[b[j]];
                        }
                        list.Add(temp);
                    }
                }
            }
            /// <summary>
            /// 递归算法求排列(私有成员)
            /// </summary>
            /// <param name="list">返回的列表</param>
            /// <param name="t">所求数组</param>
            /// <param name="startIndex">起始标号</param>
            /// <param name="endIndex">结束标号</param>
            private static void GetPermutation(ref List<T[]> list, T[] t, int startIndex, int endIndex)
            {
                if (startIndex == endIndex)
                {
                    if (list == null)
                    {
                        list = new List<T[]>();
                    }
                    T[] temp = new T[t.Length];
                    t.CopyTo(temp, 0);
                    list.Add(temp);
                }
                else
                {
                    for (int i = startIndex; i <= endIndex; i++)
                    {
                        Swap(ref t[startIndex], ref t[i]);
                        GetPermutation(ref list, t, startIndex + 1, endIndex);
                        Swap(ref t[startIndex], ref t[i]);
                    }
                }
            }
            /// <summary>
            /// 求从起始标号到结束标号的排列，其余元素不变
            /// </summary>
            /// <param name="t">所求数组</param>
            /// <param name="startIndex">起始标号</param>
            /// <param name="endIndex">结束标号</param>
            /// <returns>从起始标号到结束标号排列的范型</returns>
            public static List<T[]> GetPermutation(T[] t, int startIndex, int endIndex)
            {
                if (startIndex < 0 || endIndex > t.Length - 1)
                {
                    return null;
                }
                List<T[]> list = new List<T[]>();
                GetPermutation(ref list, t, startIndex, endIndex);
                return list;
            }
            /// <summary>
            /// 返回数组所有元素的全排列
            /// </summary>
            /// <param name="t">所求数组</param>
            /// <returns>全排列的范型</returns>
            public static List<T[]> GetPermutation(T[] t)
            {
                return GetPermutation(t, 0, t.Length - 1);
            }
            /// <summary>
            /// 求数组中n个元素的排列
            /// </summary>
            /// <param name="t">所求数组</param>
            /// <param name="n">元素个数</param>
            /// <returns>数组中n个元素的排列</returns>
            public static List<T[]> GetPermutation(T[] t, int n)
            {
                if (n > t.Length)
                {
                    return null;
                }
                List<T[]> list = new List<T[]>();
                List<T[]> c = GetCombination(t, n);
                for (int i = 0; i < c.Count; i++)
                {
                    List<T[]> l = new List<T[]>();
                    GetPermutation(ref l, c[i], 0, n - 1);
                    list.AddRange(l);
                }
                return list;
            }
            /// <summary>
            /// 求数组中n个元素的组合
            /// </summary>
            /// <param name="t">所求数组</param>
            /// <param name="n">元素个数</param>
            /// <returns>数组中n个元素的组合的范型</returns>
            public static List<T[]> GetCombination(T[] t, int n)
            {
                if (t.Length < n)
                {
                    return null;
                }
                int[] temp = new int[n];
                List<T[]> list = new List<T[]>();
                GetCombination(ref list, t, t.Length, n, temp, n);
                return list;
            }
        }

var combinePrefixKeyList = new Keys[] { Keys.Control, Keys.Alt, Keys.Shift };
            var result = new List<List<Keys>>();
            for(var i =1 ;i <= combinePrefixKeyList.Count() ;i++)
            {
                var combinationList = PermutationAndCombination<Keys>.GetCombination(combinePrefixKeyList, i);
                var items = combinationList.Select(item => item.ToList()).ToList();
                result.AddRange(items);
            }

            var keyNames = Enum.GetNames(typeof(Keys)).ToList();
            foreach (var keyName in keyNames)
                KeyList.Add(keyName, (Keys)Enum.Parse(typeof(Keys), keyName));

            var combineKeyList = (from item in result
                                  join key in KeyList.Select(k => k.Value).Except(new List<Keys> { Keys.None })
                                      on true equals true
                                  select item.Concat<Keys>(new List<Keys> { key })
                        ).ToList();

            Func<List<int>, int> GetCombinedKeyCode = null;
            GetCombinedKeyCode = delegate(List<int> args)
            {
                if (args.Count == 0)
                    return 0;

                if (args.Count == 1)
                    return args[0];

                return args[0] | GetCombinedKeyCode(args.Skip(1).ToList());
            };

            Func<int, int> GetVirtualKeyCode = delegate(int args)
            {
                return (byte)(args & 0xFF);
            };

            foreach (var item in combineKeyList)
            {
                var names = item.Select(key => Enum.GetName(typeof(Keys), key));
                var keyCombination = string.Join("+", names);
                Debug.Print(keyCombination + ":\t" + GetVirtualKeyCode(GetCombinedKeyCode(item.Cast<int>().ToList())).ToString());
            }