That's a controversial part of it. I think that strictly, if the nodes are allocated as part of one array, it is permissible to use current++ to traverse from o

That's a controversial part of it. I think that strictly, if the nodes are allocated as part of one array, it is permissible to use current++ to traverse from one to the other. While it would be UB if they are in separate allocations, even if it logically should work all the same way.