组合转排列最优算法

组合转排列，经过测试，找到一个可能是比较优秀的算法

using System;

namespace DogFramework
{
    /// <summary>
    /// 一个简单的排列
    /// </summary>
    public class SimplePermute
    {
        public void GetPermute<T>(T[] list, Action<T[]> actAddPermute)
        {
            int x = list.Length - 1;
            GetPermute<T>(list, 0, x, actAddPermute);
        }

        private void GetPermute<T>(T[] list, int k, int m, Action<T[]> actAddPermute)
        {
            if (k == m)
            {
                actAddPermute?.Invoke(list);
            }
            else
            {
                for (int i = k; i <= m; i++)
                {
                    Swap(ref list[k], ref list[i]);
                    GetPermute(list, k + 1, m, actAddPermute);
                    Swap(ref list[k], ref list[i]);
                }
            }
        }

        void Swap<T>(ref T a, ref T b)
        {
            T tmp;
            tmp = a;
            a = b;
            b = tmp;
        }

        public void Test()
        {
            string str = "ABCD";
            char[] arr = str.ToCharArray();

            GetPermute(arr, (p)=> { Console.WriteLine(p); });
            Console.ReadKey();
        }
    }
}