51nod 1027 大数乘法

#include <bits/stdc++.h>
using namespace std;

string multi(string a,string b)
{
	int arr[2020],i,j;
	memset(arr,sizeof(arr));
	reverse(a.begin(),a.end());
	reverse(b.begin(),b.end());
	for(i=0;i<a.length();i++)
	{
		for(j=0;j<b.length();j++)
		{
			arr[i+j]+=(a[i]-'0')*(b[j]-'0');
		}
	}
	string ret(a.length()+b.length(),'0');
	for(i=0;i<a.length()+b.length();i++)
	{
		arr[i+1]+=arr[i]/10;
		arr[i]%=10;
		ret[i]+=arr[i];
	}
	reverse(ret.begin(),ret.end());
	if(ret[0]=='0')
		ret=ret.substr(1);
	return ret;
}

int main()
{
	string a,b;
	while(cin>>a>>b)
	{
		cout<<multi(a,b)<<endl;
	}
}