大数据的乘法

//大数据相乘，具体的算法思想见c

#define  _CRT_SECURE_NO_WARNINGS  //vs2013去掉安全检查

#include <stdlib.h>
#include <string.h>
#include <iostream>

using namespace std;
class big_data
{
public:
    void init_string()
    {
        cout << "str1 = ";
        cin >> str1;
        cout << endl;
        cout << "str2 = ";
        cin >> str2;
        cout << endl;
    }
    char* big_data_multi ()
    {
        int length_str1 = strlen(str1);
        int length_str2 = strlen(str2);
        int *pstr3 = (int*)malloc(sizeof(int)*(length_str1+length_str2));
        memset(pstr3, 0, sizeof(int)*(length_str1+length_str2));//一定要初始化，否则乱码
        for(int i = 0; i < length_str2; i++)//循环累乘相加
        {
            for(int  j = 0;  j < length_str1; j++)
            {
                pstr3[i + j + 1] += (str1[j] - ‘0‘) * (str2[i] - ‘0‘);
            }
        }
        for (int i = length_str1 + length_str2 - 1; i >= 0; i--)
        {
            if(pstr3[i] >= 10)
            {
                pstr3[i - 1] += pstr3[i] / 10;
                pstr3[i] = pstr3[i]%10;
            }
        }
        int i = 0;
        while (pstr3[i] == 0)
        {
            i++;
        }
        char *pstr4 = (char*)malloc(sizeof(char)*(length_str1 + length_str2 + 1));
        int j = 0;
        for(; j < length_str1+length_str2 && i < length_str1+length_str2; j++,i++)
        {
            pstr4[j] = pstr3[i] + ‘0‘;
        }
        pstr4[j] = ‘\0‘;
        return pstr4;
    }
private:
    char str1[100];
    char str2[100];
};

int main()
{
    big_data bigdata1;

    while(1)
    {
        cout << endl;
        bigdata1.init_string();
        cout << "相乘的结果是 ：" << bigdata1.big_data_multi() << endl;
    }

    system("pause");
}