One way to implement a queue is to use a circularly linked list. Assume that the list does not contain a header and that you can maintain one iterator for the list. For which of the following...

One way to implement a queue is to use a circularly linked list. Assume that the list does not contain a header and that you can maintain one iterator for 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 first item in the list.

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