C job interview - casting and comparing

Question

I was confronted with a tricky (IMO) question. I needed to compare two MAC addresses, in the most efficient manner.

The only thought that crossed my mind in that moment

Answer 1

If he is really dissatisfied with this approach (which is essentially a brain fart, since you aren't comparing megabytes or gigabytes of data, so one shan't really be worrying about "efficiency" and "speed" in this case), just tell him that you trust the quality and speed of the standard library:

int isEqual(MAC* addr1, MAC* addr2)
{
    return memcmp(&addr1->data, &addr2->data, sizeof(addr1->data)) == 0;
}