大整数乘法

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

int result[200];
void mul(string n1,string n2)
{
unsigned long len1=n1.length();
unsigned long len2=n2.length();
int carry=0;
for(int k=len1+len2-2;k>=0;k--)
{
int sum=0;
for(int i=0;i<len1;i++)
{
int j=k-i;
if(j<len2&&j>=0)
{
sum=sum+(int)(n1[i]-'0')*(int)(n2[j]-'0');;
}
}
sum=sum+carry;
result[k+1]=sum%10;
carry=sum/10;
}
result[0]+=carry;
return ;
}

int main()
{
for(int i=0;i<200;i++)
{
result[i]=0;
}
string n1="100";
string n2="100";
mul(n1,n2);
for(int i=0;i<=n1.length()+n2.length()-1;i++)
{
if(i==0&&result[0]==0)
{
continue;
}
cout<<result[i];
}
cout<<endl;
return 0;
}