Is there any difference between the two (in the context of graphs)? In my mind I'm thinking that O(n + n) is the same as O(2n) which is just O(n). I can sort of understand that visiting each node more than once is worse than visiting each node just once but I'm pretty sure that would still fall under O(n).
I might be confusing with O(n + m) but I'm pretty sure I've heard of both before.