One way to implement a queue is to use a circular linked list. In a circular linked list, the last node's next pointer points at the ?rst node. Assume the list does not contain a header and that we can maintain, at most, one iterator corresponding to a node in the list. For which of the following representations can all basic queue operations be performed in constant worst-case time? Justify your answers.

a. Maintain an iterator that corresponds to the ?rst item in the list.

b. Maintain an iterator that corresponds to the last item in the list.