高精计算

 

高精计算
编写一个以字符串为基础进行整数加法的一个程序。这个整数包含符号位，总长不超过255位（因为某些语言的字符串有长度限制）。

输入文件格式：两行，每行为一个长度不超过255的十进制数。可以是负的，负号算一位，既负数的数字部分不超过254位。
in.txt
输出文件格式：一行，得数。
out.txt

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

int main()
...{
     ifstream infile("in.txt");
     ofstream outfile("out.txt");
     string s1,s2;
     getline(infile,s1);
     getline(infile,s2);
     string::iterator s_iter1(s1.begin()),s_iter2(s2.begin());
     int len,sign1(1),sign2(1),sign_ans(1);
     if (*s_iter1=='-')...{
         sign1=-1;
         s1.erase(s_iter1);
         }
     if (*s_iter2=='-')...{
         sign2=-1;
         s2.erase(s_iter2);
         }
     if (s1.size()>s2.size())
         len=s1.size();
     else
         len=s2.size();
     vector<int> ans(len+1,0),ivec1(len,0),ivec2(len,0);
     vector<int>::reverse_iterator r_iter1(ivec1.rbegin()+len-s1.size()),r_iter2(ivec2.rbegin()+len-s2.size()),r_iter_ans(ans.rbegin());
     vector<int>::iterator iter1(ivec1.begin()),iter2(ivec2.begin()),iter_ans(ans.begin());
     
     if (sign1==1)
         for (int i=0;i!=s1.size();++i,++r_iter1)
             *r_iter1=s1[i]-'0';
     else
         for (int i=0;i!=s1.size();++i,++r_iter1)
             *r_iter1='0'-s1[i];

     if (sign2==1)
         for (int i=0;i!=s2.size();++i,++r_iter2)
             *r_iter2=s2[i]-'0';
     else
         for (int i=0;i!=s2.size();++i,++r_iter2)
             *r_iter2='0'-s2[i];

     for (int i=0;i!=len;++i,++iter1,++iter2,++iter_ans)
         *iter_ans=*iter1+*iter2;
     if (*(iter_ans-1)<0)...{
         outfile<<"-";
         iter_ans=ans.begin();
         for (int i=0;i!=len;++iter_ans,++i)
             *iter_ans=-*iter_ans;
         }
     iter_ans=ans.begin();
     for (int i=0;i!=len;++iter_ans,++i)
         if (*iter_ans>0)...{
             *(iter_ans+1)+=*iter_ans/10;
             *iter_ans=*iter_ans%10;
             }
         else if (*iter_ans!=0)...{
                  --*(iter_ans+1);
                  *iter_ans+=10;
                  }

     for (;r_iter_ans!=ans.rend();++r_iter_ans)
         if ((sign_ans==1)&&(*r_iter_ans==0))
             continue;
         else...{
              sign_ans=0;
              outfile<<*r_iter_ans;
              }

     infile.close();
     outfile.close();
     return 0;
}