高精度模板

#include <bits/stdc++.h>

using namespace std;

string add(string s1,string s2)
{
    int l1 = s1.size();
    int l2 = s2.size();
    if(l2>l1)
    {
        int n = l2-l1;
        while(n)
        {
            s1 = '0'+s1;
            n--;
        }
    }
    if(l1>l2)
    {
            int n = l1-l2;
        while(n)
        {
            s2 = '0'+s2;
            n--;
        }
    }
    int cf = 0;
    int len = s1.size();
    string ss;
    for (int i=len-1;i>=0;i--)
    {
        int a = s1[i]-'0'+s2[i]-'0'+cf;
        int tmp = a%10;
        cf = a/10;

        ss= char(tmp+'0')+ss;
    }
    if(cf!=0)
    {
        ss=char(cf+'0')+ss;
    }


    //ss.erase(0,ss.find_first_not_of('0'));
    return ss;
}
bool cmp(string s1,string s2)
{
    if(s1.size()!=s2.size()) return s1.size()>s2.size();
    return s1>=s2;
}
//s1>=s2
string sub(string s1,string s2)
{
    int l1 = s1.size();
    int l2 = s2.size();
    if(l1>l2)
    {
            int n = l1-l2;
        while(n)
        {
            s2 = '0'+s2;
            n--;
        }
    }
    int cf=0;
    string ss;
    for (int i=s1.size()-1;i>=0;i--)
    {
        int tmp;
        if(s1[i]-cf>=s2[i])  {tmp = s1[i]-s2[i]-cf;cf=0;}
        else {

            tmp = s1[i]+10-s2[i]-cf;
            cf = 1;

        }
        ss= char(tmp+'0')+ss;
    }

    ss = ss.erase(0,ss.find_first_not_of('0'));
    if(ss=="") ss="0";
    return ss;
}

string mul(string s1,string s2)
{
    int l1 = s1.size();
    int l2 = s2.size();
    string str;
    for (int i=l2-1;i>=0;i--)
    {
        string suf;
        for (int k=l2-1-i;k>0;k--)
            suf+="0";
         int num = s2[i]-'0';
         int cf = 0;
        string tss;
        for (int j=l1-1;j>=0;j--)
        {
            int tmp = (s1[j]-'0')*num+cf;
            cf = tmp/10;
            tss= char(tmp%10+'0')+tss;

        }
        if(cf!=0) tss=char(cf+'0')+tss;
        str=add(str,tss+suf);
    }
        str = str.erase(0,str.find_first_not_of('0'));
    if(str=="") str="0";
    return str;
}


int main()
{

    string s1,s2;
   while(cin>>s1>>s2)
   {
       string s3 ;
        s3=mul(s1,s2);
        cout<<s3<<endl;
   }

}