c# 求一定的大阶乘

1.通过List<int> 类型存储

代码：

   private List<int> fact(int n)
       {
           int s = 1;
           int m = 0;
            int a,b,c;
           List<int> lstfact = new List<int>();
           List<int> lstresult = new List<int>();
           lstfact.Add(1);
           for (int i = 1; i <= n; i++)
           {
               m = 0;
            for (int k = 0; k < lstfact.Count;k++ )
            {
                s = i * lstfact[k];
                s = s + m;
                a = s / 10;
                b = s % 10;
                lstfact[k] = b;
                if (a>0)
                {
                    if (k<lstfact.Count-1)
                    {
                        m = a;
                    }
                    else
                    {
                        lstfact.Add(a);
                        break;
                    }
                }
                else
                {
                    m = 0;
                }
               
            }
        }
           for (int k = lstfact.Count - 1; k >= 0;k-- )
           {
               lstresult.Add(lstfact[k]);
           }
           return lstresult;
       }

2.通过字符串存储

 private string factss(int n)
        {
            int s = 1;
            int m = 0;
            int a, b, c;
            StringBuilder strb = new StringBuilder();
            StringBuilder strfac = new StringBuilder();
            strb.Append("1");
            for (int i = 1; i <= n; i++)
            {
                m = 0;
                for (int k =0; k<strb.Length; k++)
                {
                    s = i * int.Parse(strb[k].ToString());
                    s = s + m;
                    a = s / 10;
                    b = s % 10;
                    strb[k] =Convert.ToChar(b.ToString());
                    if (a > 0)
                    {
                        if (k < strb.Length - 1)
                        {
                            m = a;
                        }
                        else
                        {
                            strb.Append(a);
                            break;
                        }
                    }
                    else
                    {
                        m = 0;
                    }

                }
            }
            for (int k =strb.Length-1; k >= 0; k--)
            {
                strfac.Append(strb[k]);
            }
            return strfac.ToString();
        }