10106 Product-j3TByGHV.txt

#include<iostream>
#include<cstdio>
#include<string>
#include<algorithm>
#include<fstream>
using namespace std;
string add(string s, string str)
{
    string sum = "";

    int len1 = s.length();
    int len2 = str.length();

    reverse(s.begin(),s.end());
    reverse(str.begin(),str.end());

    int x = len1<=len2 ? len1 : len2;
    int carry = 0;int a,b,i;
    for(i=0; i<x; i++){
        a = s[i]-48;
        b = str[i]-48;
        int p = a+b+carry;
        if(p>=10){
            carry = 1;
            p%=10;
        }
        else
            carry = 0;
        sum+=(p+48);
    }
    if(len1>len2){
        for(i; i<len1; i++){
            a = s[i]-48;
            int p = a+carry;
            if(p>=10){
                carry = 1;
                p%=10;
            }
            else
                carry = 0;
            sum+=(p+48);
        }
    }
    if(len1<len2){
        for(i; i<len2; i++){
            a = str[i]-48;
            int p = a+carry;
            if(p>=10){
                carry = 1;
                p%=10;
            }
            else
                carry = 0;
            sum+=(p+48);
        }
    }
    if(carry == 1)
        sum+=(carry+48);
    reverse(sum.begin(),sum.end());
    return sum;
}
string normalize(string s)
{
    if(s[0]!='0')
        return s;
    int len = s.size();
    reverse(s.begin(),s.end());
    for(int i=len-1; i>0 && s[i]=='0'; i--){
        s.erase(s.begin() + i);
    }

    if(s.size()==0)
        s = "0";
    else
        reverse(s.begin(),s.end());

    return s;
}
string multiply(string a, string b)
{
    string product = "";
    int len = a.size() - 1 ;
    while(len>=0){
        int p = a[len]-48;
        int i;
        string temp = "0";
        for(i=1; i<=p; i++){
            temp = add(temp, b);
        }
        product  = add(product , temp);
        b = b + "0";
        len--;
    }
    product = normalize(product);
    return product;
}
int main()
{
    string a,b;

    while(cin>>a>>b){
       cout<<multiply(a,b)<<endl;
    }

    return 0;
}