c++求大牛指点，都是紫的！！！

#include<iostream>
#include<string>
using namespace std;
int main()
{
    string as,bs,ts;
    int a[100001]={0},b[100001]={0},c[100001]={0},la,lb,lc;
    cin>>as>>bs;
    la=as.size();lb=bs.size();
    for(int i=1;i<=la;i++) 
      a[i]=as[la-i]-'0';
    for(int i=1;i<=lb;i++) 
      b[i]=bs[lb-i]-'0';
    for(int i=1;i<=la;i++)
      for(int j=1;i<=lb;j++)
        c[i+j-1]+=a[i]*b[j];
    lc=la+lb-1;
    for(int i=1;i<=lc;i++)
      if(c[i]>9){c[i+1]+=c[i]/10;c[i]%=10;}
    while(c[lc]) lc++;
    for(int i=lc-1;i>=1;i--) cout<<c[i];
    return 0;
}