渣渣写算法之丢手帕问题

约瑟夫问题（丢手帕）

下面是尝试的一些Demo写法，先不要在意代码上的细节

① 利用数组，还是这个块，因为数据结构简单

  public static void ThreeOut(int num, int outnum)
        {          
            int[] data = new int[num];
            for (int i = 0; i < num; i++)
            {
                data[i]=i + 1;
            }          
            int index = 0;
            int count = 0;
            for (int i = 0; ; i++)
            {
                if (index >= data.Length)
                {
                    index = 0;
                }

                if (data[index] == 0)
                {
                    i--;
                    index++;
                    continue;
                }
                if ((i + 1) % outnum == 0)
                {
                  //  Console.WriteLine(data[index]);  输出每一个
                    if (count >= data.Length - 1)
                    {
                        Console.WriteLine($"最后一个{ data[index]}");  //输出最后一个
                        break;
                    }
                    count++;
                    data[index] = 0;
                }
                index++;
            }
        }

②利用List，没有数组快

   public static void Second(int num,int outnum)
        {
            List<int> data = new List<int>();
            for (int i = 0; i < num; i++)
            {
                data.Add(i+1);
            }
            int index = 0;
            for (int i = 0;; i++)
            {
                if (index>= data.Count)
                {
                    index = 0;
                }
                if (data.Count==1)
                { 
                    Console.WriteLine($"最后一个{data[0]}"); //输出最后一个
                    break;
                }                

                if ((i + 1) % outnum == 0)
                {
                    // Console.WriteLine(data[index]); //输出每一个
                    data.Remove(data[index]);
                }
                else {
                    index++;
                }               
            }
        }

③ 环形链表，慢

private static void FirstOut(List<HHH> data,int num, int outnum)
        {
          
            int index = 0;
            for (int i = 0; ; i++)
            {
                if (data.Count <= 0)
                {
                    break;
                }

                if (index > 0)
                {
                    if (index >= data.Count)
                    {
                        index = 0;
                    }
                    data[index].Index = i + 1;
                }

                if (data[index].Index % outnum == 0)
                {
                    //   Console.WriteLine(data[index].Name); //输出每一个
                    if (index == 0)
                    {
                        data[data.Count - 1].Next = data[index].Next;
                    }
                    else
                    {
                        data[index - 1].Next = data[index].Next;
                    }
                    if (data.Count <= 1)
                    {
                        Console.WriteLine($"最后一个{data[index].Name}");
                        data.Remove(data[index]);
                        break;
                    }
                    else {
                        data.Remove(data[index]);
                    }                   
                }
                else
                {
                    index++;
                }
            }
        }

  private static List<HHH> CreateList(int num)
        {
            var first = new HHH()
            {
                Index = 1,
                Name = $"小孩1",
            };
            List<HHH> data = new List<HHH>() { first };
            for (int i = 2; i <= num; i++)
            {
                var item = new HHH()
                {
                    Name = $"小孩{i}",
                };
                data.Add(item);
                data[i - 2].Next = item;
            }
            data.Last().Next = first;
            return data;
        }

简单测试

  static void Main(string[] args)
        {
            int num = 50000;
            int outnum = 72;
            Stopwatch st = new Stopwatch();
            st.Start();
            Two.Second(num, outnum);

            st.Stop();
            Console.WriteLine($"List耗时:{st.ElapsedMilliseconds}");
            st.Reset();
            st.Start();
            Three.ThreeOut(num, outnum);
            st.Stop();
            Console.WriteLine($"数组耗时:{st.ElapsedMilliseconds}");
             st.Reset();
            List<HHH> data = CreateList(num);
            st.Start();
            //for (int i = 0; i < 300; i++)
            //{          
            FirstOut(data,num, outnum);
            //}
            st.Stop();
            Console.WriteLine($"环形耗时:{st.ElapsedMilliseconds}");

            Console.ReadKey();
     }

 所以优先使用简单的结构解决问题