大数乘法

#include <iostream>
 #include <string>
  using namespace std;
  
  void multiply (const char *a,const char *b){
 int i,j,la,lb;
 la=strlen(a);
 lb=strlen(b);
  int *s=(int *)malloc(sizeof(int)*(la+lb));
 //int*s=new int[la+lb];
 for(i=0;i<=la+lb-1;i++)  s[i]=0;//初始化
 for(i=0;i<la;i++){
 for(j=0;j<lb;j++)
 s[i+j+1]+=(a[i]-'0')*(b[j]-'0');
 }
 for(i=la+lb-1;i>=0;i--){//实现移位
 s[i]=s[i]%10;
 s[i-1]+=s[i]/10;
 }

 int tag=0;
 for(i=0;i<la+lb;i++){
 if(s[i]==0&&tag==0) tag=1;
     else cout<<s[i];
 }
 cout<<endl;
 
 }
  
   
int main(){
 string num1,num2;
 cout<<"plesea put in the two number"<<endl;
 cin>>num1>>num2;
 const char *p1=num1.c_str();
          const char *p2=num2.c_str();
          multiply(p1,p2);
 return 1;
 }