COSC 311 WINTER 2013  Queue basic ops on linked list (see your text!!)

(1) Note! head == tail will be true for two cases:
     queue empty, and
     queue has one element.
     
     So, use the following to distinguish these cases:
     if (head == null) {
     	// queue empty
     	}
     else if (head == tail) {
     	// queue has one element
     	}
     else {
     	// queue has more than one element
     	}


(2) insert to a queue with one or more elements:
	insert(d)  --> use the following:
		
		Node n = new Node(d);
		tail.next = n;
		tail = n;
		
(3) delete from a queue with more than one element:
	delete()  --> use the following:
	
		Node n = head;
		head = head.next;
		return n;
		
(4) Note, for other cases (e.g., empty queue), you will do slightly different
 operations to insert/delete.