Integer division without using the / or * operator

Question

I am going through an algorithms and datastructures textbook and came accross this question:

1-28. Write a function to perform integer division withou

Answer 1

I don't know what you mean by fast...and this seems like a basic question to test your thought process.

A simple function can be use a counter and keep subtracting the divisor from the dividend till it becomes 0. This is O(n) process.

int divide(int n, int d){
    int c = 0;
    while(1){
        n -= d;
        if(n >= 0)
            c++;
        else
            break;
    }
    return c;
}

Another way can be using shift operator, which should do it in log(n) steps.

    int divide(int n, int d){
    if(d <= 0)
        return -1;
    int k = d;
    int i, c, index=1;
    c = 0;
    while(n > d){
        d <<= 1;
        index <<= 1;
    }
    while(1){
        if(k > n)
            return c;
        if(n >= d){
            c |= index;
            n -= d;                
        }
        index >>= 1;
        d >>= 1;
    }
    return c;
}

This is just like integer division as we do in High-School Mathematics.

PS: If you need a better explanation, I will. Just post that in comments.

EDIT: edited the code wrt Erobrere's comment.