Refactor (rewrite) our queue data structure so that, instead of using a doubly-linked list, it

instead uses a singly-linked list and pointer to the last list node. The time complexity of all

operations in your list should match those in Table 4.7. Which variant do you prefer, and

why?

revu class Queue: def __init__(self): self.linked_list = LinkedList() def __len__(self): return len(self.linked_list) def __iter__(self): return iter(self.linked_list) def front(self): return self.linked_list.first() def enqueue (self,x): self.linked_list.add_last(x) def dequeue (self): x = self.front() self.linked_list.remove_first() return x Pseudocode queue = Queue () len(queue) iter(queue) Time Complexity O(1) O(1) 0(1) Queue Operation Create an empty queue Get the length of a queue Get an iterator for the elements in front- to-back order Get the element at the front of a non- empty queue Add element to the back Remove and return the element at the front x = queue.front() 0(1) queue. enqueue (x) x = stack. dequeue () 0(1) 0(1) Table 4.7: Queue Operations