We have chosen to implement the cinema queue as a singly linked list of nodes. Note: this is not an indication of whether singly linked lists were the correct or incorrect solution to part (a).

A node includes a customer and their priority value. You can see our (partial) implementation here:

class CinemaPriorityQueue: """A linked list implementation of an unbounded min-priority queue.""" class Node: """A node in a linked list.""" def __init__(self, item: object, priority_value: int) -> None: """Initialise the node with the given item and priority value.""" self.item = item self.priority = priority_value self.next = None def __init__(self) -> None: """Initialise the queue to be empty.""" self.head = None def is_empty(self) -> bool: """ Preconditions: true Postconditions: the output is true if the queue is empty, false otherwise """ return self.head == None def insert(self, item: object, priority_value: int) -> None: """Insert item according to priority. Preconditions: true Postconditions: post-self is the sequence pre-self with item inserted after the last item in self with the same priority value """ pass 

Remember that the application implements an unbounded min-priority queue. The highest priority has priority value 1 and the lowest priority has priority value 4.

Sketch an algorithm (not Python code) to implement the insert function.

You need to consider the following cases:

• insert into an empty queue
• insert at the front of the queue
• insert after some existing node.

Write your answer here

(c) (10 marks)

Edit the insert function in the code below to convert your algorithm into Python code. You must observe the coding style guidance in Chapter 5.3 and Chapter 10.3.

In [ ]:

class CinemaPriorityQueue:

 """A linked list implementation of an unbounded min-priority queue."""

 class Node:

 """A node in a linked list."""

 def __init__(self, item: object, priority_value: int) -> None:

 """Initialise the node with the given item and priority value."""

 self.item = item

 self.priority = priority_value

 self.next = None

 def __init__(self) -> None:

 """Initialise the queue to be empty."""

 self.head = None

 def is_empty(self) -> bool:

 """

 Preconditions: true

 Postconditions: the output is true if the queue is empty, false otherwise

 """

 return self.head == None

 def print(self) -> None:

 """Print out the queue"""

 if self.head == None:

 print('The queue is empty')

 else:

 current = self.head

 while current != None:

 print(current.item, current.priority)

 current = current.next

 def insert(self, item: object, priority_value: int) -> None:

 """Insert item according to priority.

 Preconditions: true

 Postconditions: post-self is the sequence

 pre-self with item inserted after

 the last item in self with the same priority

 """

 pass

 #*Write your code solution here*