高精度

输入的两个数要求为正。 

#include<stdio.h>
#include<string>
#include<string.h>
#include<iostream>
#include<cmath>
using namespace std;

int compare(string str1,string str2)
{
    if(str1.length() > str2.length())    return 1;
    else if(str1.length() < str2.length())    return -1;
    else    return str1.compare(str2);
}

string add(string str1,string str2)//加法 
{
    string str;
    int len1 = str1.length(),len2 = str2.length();
    if(len1 < len2)
    {
        for(int i = 1;i <= len2-len1;i++)    str1 = "0"+str1;
    }
    else
    {
        for(int i = 1;i <= len1-len2;i++)    str2 = "0"+str2;
    }
    int cf = 0,temp;
    for(int i = str1.length()-1;i >= 0;i--)
    {
        temp = str1[i]-'0'+str2[i]-'0'+cf;
        cf = temp/10;
        temp %= 10;
        str = char(temp+'0')+str;
    }
    if(cf != 0)    str = char(cf+'0')+str;
    return str;
}

string sub(string str1,string str2)//减法 
{
    string str;
    int flag = 0;
    if(compare(str1,str2) < 0)
    {
        flag = 1;
        swap(str1,str2);
    }
    int tmp = str1.length()-str2.length(),cf = 0;
    for(int i = str2.length()-1;i >= 0;i--)
    {
        if(str1[tmp+i] < str2[i]+cf)
        {
            str = char(str1[tmp+i]-str2[i]-cf+'0'+10)+str;
            cf = 1;
        }
        else
        {
            str = char(str1[tmp+i]-str2[i]-cf+'0')+str;
            cf = 0;
        }
    }
    for(int i = tmp-1;i >= 0;i--)
    {
        if(str1[i]-cf >= '0')
        {
            str = char(str1[i]-cf)+str;
            cf = 0;
        }
        else
        {
            str = char(str1[i]-cf+10)+str;
            cf = 1;
        }
    }
    str.erase(0,str.find_first_not_of('0'));
    if(str.empty())   str = "0";
    if(flag)    str = "-"+str;
    return str;
}

string mul(string str1,string str2)//乘法 
{
    string str;
    int len1 = str1.length();
    int len2 = str2.length();
    string tempstr;
    for(int i = len2-1;i >= 0;i--)
    {
        tempstr = "";
        int temp = str2[i]-'0',t = 0,cf = 0;
        if(temp != 0)
        {
            for(int j = 1;j <= len2-1-i;j++)    tempstr += "0";
            for(int j = len1-1;j >= 0;j--)
            {
                cf = (temp*(str1[j]-'0')+cf);
                t = cf%10;
                cf /= 10;
                tempstr = char(t+'0')+tempstr;
            }
            if(cf != 0) tempstr = char(cf+'0')+tempstr;
            str=add(str,tempstr);
        }
    }
    str.erase(0,str.find_first_not_of('0'));
    if(str.empty())   str = "0";
    return str;
}


void div(string str1,string str2,string &quotient,string &residue)//除法取余 
{
    quotient = "";
    residue = "";
    if(str2 == "0")
    {
        quotient = "ERROR";
        residue = "ERROR";
        return;
    }
    if(str1 == "0")
    {
        quotient = "0";
        residue = "0";
        return;
    }
    int res = compare(str1,str2);
    if(res < 0)
    {
        quotient = "0";
        residue = str1;
        return;
    }
    else
    {
        int len1 = str1.length();
        int len2 = str2.length();
        string tempstr;
        tempstr.append(str1,0,len2-1);
        for(int i = len2-1;i < len1;i++)
        {
            tempstr = tempstr+str1[i];
            tempstr.erase(0,tempstr.find_first_not_of('0'));
            if(tempstr.empty())    tempstr = "0";
            for(char ch = '9';ch >= '0';ch--)
            {
                string str,tmp;
                str = str+ch;
                tmp = mul(str2,str);
                if(compare(tmp,tempstr) <= 0)
                {
                    quotient = quotient+ch;
                    tempstr = sub(tempstr,tmp);
                    break;
                }
            }
        }
        residue = tempstr;
    }
    quotient.erase(0,quotient.find_first_not_of('0'));
    if(quotient.empty()) quotient="0";
}

int main()
{
     string str1,str2;
     string str3,str4;
     while(cin>>str1>>str2)
     {
         div(str1,str2,str3,str4);
         cout<<add(str1,str2)<<' '<<sub(str1,str2)<<' '<<mul(str1,str2)<<' '<<str3<<' '<<str4<<endl;;
     }
     return 0;
}