Instructions:

SLLQueue (13 pts)

● Using the three properties below, implement the

queue interface using the SLLNode class fromLab 2:

○ head_node → SLLNode object or None

○ tail_node → SLLNode object or None

○ size → int, keep track of queue size

● Implement enqueue( ),dequeue( ), front( )

● Use SLLNode methods:

get_item( ), set_item( ), get_next(), set_next( )

● (5 pts) Inenqueue(item):

â—‹ Add new SLLNode (with item) after tail_node

â—‹ Update tail_node and size properties

â—‹ If first item, update head_node property too

● (6 pts) In dequeue( ):

â—‹ If empty, raise Exception('Empty queue: cannot dequeue')

â—‹ Remove head node and return its item

â—‹ Remove any links from old head node

â—‹ Update head_node and size properties

â—‹ If queue becomes empty, reset head_node, tail_node

● (2 pts) In front( ):

â—‹ If empty, raise Exception(Empty queue: no front')

○ Return head node’s item

Code:

class SLLQueue:
   def __init__(self):
       # NOTE: DO NOT EDIT THIS CODE
       # constructor: set propertieshead_node, tail_node, size
       self.head_node = None
       self.tail_node = None
       self.size = 0

   def __repr__(self):
       # NOTE: DO NOT EDIT THIS CODE
       # string representation of SLLQueueobject
       display = []
       node = self.head_node
       while node != None:
          display.append(str(node.get_item()))
           node =node.get_next()
       display = ', '.join(display)
       return 'front [' + display +']'

   def is_empty(self):
       # NOTE: DO NOT EDIT THIS CODE
       # check if queue is empty
       return self.size == 0

   def enqueue(self,item):
       # TODO: Write your codehere...
       # TODO: add new node (with item)after tail_node
       # TODO: update tail_node and sizeproperties
       # TODO: if this is the first nodeadded, update head_node too
      
       pass # TODO: remove this line
      
   def dequeue(self):
       # TODO: Write your codehere...
       # TODO: if empty, raiseException('Empty queue: cannot dequeue')
       # TODO: remove head_node and returnits item
       # TODO: remove any links from oldhead_node (Hint: set to None)
       # TODO: update head_node and sizeproperties
       # TODO: if queue becomes empty,reset head_node and tail_node
      
       pass # TODO: remove this line

   def front(self):
       # TODO: Write your codehere...
       # TODO: if empty, raiseException('Empty queue: no front')
       # TODO: return head_node's item

       pass # TODO: remove thisline