Any faster intersection method?

I'm trying to intersect ArrayA and ArrayB values and put them into ArrayC. Is there any faster method than this?

Code:

 
 while (i<ArrayA_size && j<ArrayB_size) {
    if (ArrayA[i] == ArrayB[j]) {
      ArrayC[index++] = ArrayA[i];
      i++;
      j++;
    }
    else if (ArrayA[i] < ArrayB[j]) {    
	i++;
    }
    else
      j++;
  }

Thanks for your help!

>Is there any faster method than this?
Trusting that both your sets are sorted, O(M + N) is about the best you're going to get for a straight intersection, and that's what you've got right now. Why, are you having performance issues? Or is this some misguided attempt at premature eja^H^H^Hoptimization?

yea, i'm having optimization issues. my program spent about 40% of the total running time on this function, so i'm thinking on how to improve it

this may or may not help much -- removed array indexing

Code:

while (i<ArrayA_size && j<ArrayB_size) {
    int a = ArrayA[i];
    int b = ArrayB[j];
    if (a == b) {
      ArrayC[index++] = a;
      i++;
      j++;
    }
    else if (a < b) {    
	i++;
    }
    else
      j++;
  }

Okay, then if this isn't homework, let's try set_intersection and see if it does any better. The standard library is more likely to have a highly tuned algorithm than your handrolled version.

does array indexing slows down access? I will try it out. Thanks guys for your suggestions.
This is my job. Now I need to optimize my program, which is even harder than to make the program work. There is 2 ways I'm tackling it now. First is to improve the algorithm and coding details. Second is to implement memory management into the program.
Any comments on it?

for the set_intersection, it puts the result in the iterator result. I declare an array and put this array address in the iterator result, but how do I know how many elements are there in the result?
right now, after finish intersecting, i use a while loop to read the array to count the number of elements in the result

After hours of trying, I find a solution, hee.....

Code:

inline int Transactiondb::CreateSubg(int *set, int setcount, int *set_sub, structtid *r) {
int i=0, j=0, index=0, *add;

add = set_intersection(set, set+setcount, r->tidptr, r->tidptr+(r->transnum), set_sub);

index = (add - set_sub)-1 / sizeof(int); // since add is the last pointer in set_sub
  
  return index;
}