高精度除法

Posted 2021-03-06 es-war

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

const int Max = 550;
void Enlarge(int p[], int q[], int bits); //将数组p的数字串右移bits位
int Compare(int a[], int b[]); //比较大小
void Subtract(int a[], int b[]); //数组减法

int main()
{
    int a[Max] = {0}, b[Max] = {0}, c[Max] = {0};
    string str1, str2;
    cin >> str1 >> str2;
    int len1 = str1.size(), len2 = str2.size(), len = len1 - len2 + 1, i;
    a[0] = len1;
    b[0] = len2;
    c[0] = len;
    for (i = 1; i <= len1; i ++)
      a[i] = str1[len1 - i] - ‘0‘;
    for (i = 1; i <= len2; i ++)
      b[i] = str2[len2 - i] - ‘0‘;
    if (Compare(a, b) == -1)
      cout << "0"; 
    else
    {
        for (i = c[0]; i > 0; i --)
        {
            int  t[Max] = {0};
            Enlarge(b, t, i);
            while( Compare(a, t) >= 0)
            {
                c[i] ++;
                Subtract(a, t);
            }
        }
        while(c[0] > 0 && c[c[0]] == 0)
          c[0] --;
        for (i = c[0]; i > 0; i --)
          cout << c[i];
    }        
    return 0;
} 

void Enlarge(int p[], int q[], int bits)
{
    for (int i = 1; i <= p[0]; i ++)
      q[i + bits - 1] = p[i];
    q[0] = p[0] + bits - 1; //q[0]存储的数字串的位置 
}

int Compare(int a[], int b[])
{
    int i;
    if (a[0] > b[0])  //a的位数 > b的位数， 则a > b 
      return 1;
    else if (a[0] < b[0])  //a的位数 < b的位数， 则a < b 
      return -1;
    for (i = a[0]; i > 0; i --)
    {
        if (a[i] > b[i])
          return 1;
        else if (a[i] < b[i])
          return -1;
    }
    return 0; // 两数相等 
}

void Subtract(int a[], int b[])
{
    int flag , i;
    flag = Compare(a, b);
    if (flag == 0)
      a[0] = 0;
    else if (flag == 1)
    {
        for (i =1; i <= a[0]; i ++)
        {
            a[i] = a[i] - b[i];
            if (a[i] < 0)
            {
                a[i] += 10;
                a[i + 1] --;
            }
        }
        while(a[0] > 0 && a[a[0]] == 0)   //去掉高位多余的0，同时修正a的位数  
          a[0] --;
    }
}

 参考https://blog.csdn.net/chuanzhouxiao/article/list/2博主的文章