大数除法.txt

再发个大数除法

  #include <iostream>
#include <string>
using namespace std;

class BigNum
{
   string BNstr;
public:
   BigNum() {}
   BigNum(string s)
   {
       BNstr = s;
   }
   void setNum(string n)
   {
       BNstr = n;
   }
   int subtraction(string s)
   {
       int len, lenS, i, a, b, tmp = 0;

       // 去掉多餘的數字０
       len = BNstr.length();                // 讀取被減數的長度
       lenS = s.length();                    // 讀取減數的長度
       for (i = 0; i < len-1; i++)
           if (BNstr[0] == '0')
               BNstr.erase(BNstr.begin());
           else
               break;
       for (i = 0; i < lenS-1; i++)
           if (s[0] == '0')
               s.erase(s.begin());
           else
               break;

       len = BNstr.length();                // 讀取被減數的長度
       lenS = s.length();                    // 讀取減數的長度

       if (len == lenS && BNstr < s)
           return 0;

       if (len >= lenS) {
           for (i = 0; i < len; i++) {
               a = BNstr[len-1-i]-'0';
               if (i < lenS)
                   b = s[lenS-1-i]-'0';
               else
                   b = 0;

               if (a+tmp >= b) {
                   BNstr[len-1-i] = (a+tmp-b)+'0';
                   tmp = 0;
               }
               else {
                   BNstr[len-1-i] = (a+10+tmp-b)+'0';
                   tmp = -1;
               }
           }

           // 去掉多餘的數字０
           for (i = 0; i < len-1; i++)
               if (BNstr[0] == '0')
                   BNstr.erase(BNstr.begin());
               else
                   break;
       }
       else
           return 0;
       return 1;
   }
   string division(string s)                // 除法
   {
       string quotient = "0", divisor;
       int len, lenS, lenQ, i, j;

       // 去掉多餘的數字０
       len = BNstr.length();                // 讀取被除數的長度
       lenS = s.length();                    // 讀取除數的長度
       for (i = 0; i < len-1; i++)
           if (BNstr[0] == '0')
               BNstr.erase(BNstr.begin());
           else
               break;
       for (i = 0; i < lenS-1; i++)
           if (s[0] == '0')
               s.erase(s.begin());
           else
               break;

       len = BNstr.length();
       lenS = s.length();

       i = len-lenS;
       while (len > lenS || len == lenS && BNstr >= s) {
           divisor = s;
           for (j = 0; j < i; j++)
               divisor.append("0");
           for (j = 0; subtraction(divisor); j++);
           quotient.insert(quotient.end(),j+'0');

           len = BNstr.length();
           lenS = s.length();
           i--;
       }
       for (; i >= 0; i--)
           quotient.append("0");

       // 刪除不要的数字０
       for (i = 0; i < len-1; i++)
           if (BNstr[0] == '0')
               BNstr.erase(BNstr.begin());
           else
               break;
       lenQ = quotient.length();
       for (i = 0; i < lenQ-1; i++)
           if (quotient[0] == '0')
               quotient.erase(quotient.begin());
           else
               break;
       return quotient;
   }
   string mod()
   {
       return BNstr;
   }
};

int main()
{
   BigNum num;
   string n, n2;

   cout << "请输入被除数：";
   cin >> n;
   cout << "请输入除数：";
   cin >> n2;

   num.setNum(n);
   cout << "\n商数：";
   cout << num.division(n2);
   cout << "\n余数：" << num.mod();
   cout << endl;
   system("pause");
   return 0;
}