Answer from cs61c-eq (Nicholas Hwang 16732453) for Question 4
By reference count, no; there will always be pointers to at least one node in the structure so it cannot be successfully removed since reference count requires that there be no pointers to a structure that is to be removed. Mark and sweep would work since all pointers are followed to reachable objects which are subsequently marked as reachable; all unmarked objects are removed. If nothing else points to this structure, then none of the items in it will be marked and the memory can be successfully reclaimed.