1024位大数运算(一)

近来刚完成了1024位大数运算，拿出来跟大家分享一下。有什么不对的地方希望大家指出来，感激不尽。。。

下面是源代码，借用肖老师的话：一家之代码，欢迎拍砖。。。

#define  MAXLENGTH  (1024)  //最大位数1024*8
#define  P    0   //为正数
#define  N    1   //为负数
#define  UPPERBOUND  100000000 //进制
class BigInt
{
private:

          bool   m_bSign;    //符号位
          unsigned int m_nLength;    //数组长度
          unsigned int m_nValue[MAXLENGTH]; //存储UPPERBOUND进制的每一位的值
public: 
          BigInt();
          BigInt(char* str);
          BigInt(unsigned long Num);

         void Zero();       //将大数置零
         void Set(unsigned long Num);   //把大数设置成Num
         void Set(BigInt);     
         //字符串与大数的转换
         bool GetBigInt(char* str);   //将字符串str转换为大数
         void PutBigInt(char* str);   //将大数转换为字符串
         //加减乘除幂
         int  Mod(_int64);     //求模运算，参数为64位无符号整型
         BigInt Add(BigInt);     
         BigInt Sub(BigInt);
         BigInt Mul(BigInt);
         BigInt Div(unsigned int,unsigned int* M =NULL);//除法运算，M为余数
         bool Comp(BigInt);     //比较两个大数，大于等于为正，小于为负
         BigInt Power(BigInt);     //求幂运算，但由于位数的限制，指数实际上不可以很大

         //会改变数据成员的值
         void Add(unsigned int);
         BigInt Mul(_int64);
         BigInt Sub(unsigned int);
         bool EqulZero();      //判断是否等于零
};
//-------------------------构造函数-----------------------------------
BigInt::BigInt()
{
       this->Zero();
}
BigInt::BigInt(char* str)
{
       this->GetBigInt(str);
}
BigInt::BigInt(unsigned long Num)
{
       this->Set(Num);
}

//-------------------------设置成员变量的函数----------------------------
void BigInt::Zero()
{
      this->m_bSign = P;
      this->m_nLength = 1;
      for(int i=0; i<MAXLENGTH; i++)
              this->m_nValue[i] = 0;
}
void BigInt::Set(unsigned long Num)
{
        this->m_bSign = P;
        this->m_nLength = 1;
        this->m_nValue[0] = Num;
}
void BigInt::Set(BigInt A)
{
          this->m_bSign = A.m_bSign;
          this->m_nLength = A.m_nLength;
          for(int i=0; i<A.m_nLength; i++)
                    this->m_nValue[i] = A.m_nValue[i];
}
bool BigInt::EqulZero()
{
         if((this->m_nLength == 1)&&(this->m_nValue[0] == 0))
                   return true;
         return false;
}

//将字符串str转换为大数
bool BigInt::GetBigInt(char* str)
{
         int i = 0;
         int length = 0;    //记录字符串的长度
         for(i=0;str[i] != '/0'; i++)
                length++;
         this->Zero();
         //字符串为空
         if(length ==0)
         return true;
 
         if(str[0] == '-')  //开头为负号
         {
                this->m_bSign = N;
                i = 1;
         }
        else
        {

                i = 0;
                this->m_bSign = P;
         }
         //去掉开头多余的零
         while( (str[i] == '0')&&(i<length) )
                  i++;
         if(i == length)  //如果都是零
         {
                 this->Set(0);
                 return true;
          }
         //确定大数的长度，数组的每个元素可以表示8位的整数
         if( length%8 == 0 )
                 this->m_nLength = length/8;
         else
                 this->m_nLength = length/8 + 1;

          for(;i<length; i++)   //从第一个非零值开始转换
          {
                 Set(Mul(10));   
                 if((str[i] >='0')&& (str[i] <= '9'))
                         Add(str[i]-'0');
                 else
                 {
                         cerr<<"不识别符号！"<<endl;
                         this->m_nLength = 1;
                         this->m_nValue[0] = 0;
                         return false;
                  }
           }
          return true;
}
//将大数转换为字符串
void BigInt::PutBigInt(char* str)
{
         if(this->EqulZero())
         {
               str[0] = '0';
               str[1] = '/0';
               return ;
         }
        int k = 0;
        _int64 km = 0;
        char* temp = new char[this->m_nLength*8];
        for(int i=0; i<this->m_nLength; i++)
        {
               km = this->m_nValue[i];
               for(int j=0; j<8; j++)  //除十求余转换，直到被除数为零（可以除十转换是因为设置成了100000000进制）
               {
                         if(this->m_nValue[i] != 0)
                         {
                                    temp[k] = km%10 + '0';
                                    k++;
                                    if( (km = km/10) == 0)
                                               break;
                         }
                         else
                         {
                                    temp[k] = '0';
                                    k++;
                         }

                }
         }
 

 //将temp中倒序储存的字符逆序放入str中
         if(this->m_bSign == N)
         {
                  str[0] = '-';
                  for(i=1;k-i>=0; i++)
                  str[i] = temp[k-i];
         }
         else
         {
                  for(i=0;k-i>=0; i++)
                         str[i] = temp[k-1-i];
          }
         str[i] = '/0';

}