两个数特别大，相乘起来超过了long int型的范围？怎么计算？
比如：要计算123456789987654321 * 987654321123456的值，怎么写程序？
/* large_num_operation.cpp */
#include <iostream>
#include <cstring>using namespace std;void calc_result(string first, string second);int main()
{// 0. 定义并输入两个字符串string first;cout<<"Input number1:"<<endl;cin>>first;string second;cout<<"Input number2:"<<endl;cin>>second;calc_result(first, second);return 0;
}void calc_result(string first, string second)
{// 1. 记录两个字符串长度int flen = first.size();int slen = second.size();int result[flen+slen]; // 定义数组存储每一位运算结果// 2. 初始化数组memset(result, 0, sizeof(result));// 3. 相乘for(int i=0; i<flen; i++){for(int j=0; j<slen; j++){result[i+j+1] += (first.at(i)-'0')*(second.at(j)-'0');}}// 4. 进位for(int i=flen+slen-1; i>=0; i--){if(result[i] >= 10){result[i-1] += result[i]/10;result[i] = result[i]%10;}}// 5. 输出cout<<endl<<"The result: "<<endl;int i=0;while(result[i]==0){i++;}; // 若以0开头，去掉0for(; i<flen+slen; i++){cout<<result[i];if ( i != (flen+slen-1) && (flen+slen-1-i)%3 == 0 )cout<<",";}cout<<endl;
}
