Question

Please add the following method as a part of the UnorderedList class definition:

•print_list:

the method prints the elements of the

list using the same format as a Python list

(square brackets and commas as separators).

In the main function of the modified UnorderedList.py, please test the new method to demonstrate that it works as expected.

Please leave comments in the code to show what is done

UnorderList.py file

# Implementation of an Unordered List ADT as a linked list. The list

# is accessed through a reference to the first element, head.  

# Adopted from Section 3.9 of the textbook.

from Node import Node

class UnorderedList:

  '''

  List is empty upon creation and the head reference is None

  '''

  def __init__(self):

    self.head = None   

     

  '''

  Returns True if list is empty, False otherwise

  '''

  def is_empty(self):

    return self.head == None

   

  '''

  Add an element to head of the list

  '''

  def add(self, item):

    # Create a node using item as its data

    temp = Node(item)

    # make the next reference of the new node refer to the head

    # of the list

    temp.set_next(self.head)

    # modify the list head so that it references the new node

    self.head = temp

     

  '''

  Returns the size of the list

  '''

  def size(self):

    # start at the head of the list

    current = self.head

    count = 0

    # Traverse the list one element at a time. We know

    # we reached the end when the next reference is None

    while current != None:

      count = count + 1

      current = current.get_next()

    return count

  '''

  Search for an item in the list. Returns True if found, False otherise.  

  '''

  def search(self,item):

    current = self.head

    found = False

    # As long as the element is not found and we haven't

    # reached the end of the list

    while current != None and not found:

      if current.get_data() == item:

        found = True

      else:

        # go to the next element

        current = current.get_next()

    return found

   

  '''

  Remove the first occurrence of item from the list.  

  '''

  def remove(self, item):

    # keep track of current and previous elements

    current = self.head

    previous = None

    found = False

    # traverse the list

    while current != None and not found:

      # if we have a match, stop

      if current.get_data() == item:

        found = True

      # otherwise advance current and next references

      else:

        previous = current

        current = current.get_next()

      

    # the element to be deleted is the head of the list   

    if found:

      if previous == None:

        self.head = current.get_next()

        # the element to be deleted is not the head

      else:

        previous.set_next(current.get_next())

      

      

def main():

  # create a list and add some elements to it

  aList = UnorderedList()

  print("Adding 3, 5, 8, and 11 to the list.")

  aList.add(3)

  aList.add(5)

  aList.add(8)

  # 11 is the head of the list

  aList.add(11)

   

  print("List size:", aList.size())

  print("Is 5 in the list? ", aList.search(5))

  print("Removing 5 from the list.")

  aList.remove(5)

  print("Is 5 in the list? ", aList.search(5))

  print("List size:", aList.size())

  print("Removing 3 from the list.")

  aList.remove(3)   

  print("List size:", aList.size())

  

if __name__ == "__main__":

  main()

Answer 1

Here is a python code with implementation of print_list() method :

from Node import Node

class UnorderedList:

  '''

  List is empty upon creation and the head reference is None

  '''

  def __init__(self):

    self.head = None   

     

  '''

  Returns True if list is empty, False otherwise

  '''

  def is_empty(self):

    return self.head == None

   

  '''

  Add an element to head of the list

  '''

  def add(self, item):

    # Create a node using item as its data

    temp = Node(item)

    # make the next reference of the new node refer to the head

    # of the list

    temp.set_next(self.head)

    # modify the list head so that it references the new node

    self.head = temp

     

  '''

  Returns the size of the list

  '''

  def size(self):

    # start at the head of the list

    current = self.head

    count = 0

    # Traverse the list one element at a time. We know

    # we reached the end when the next reference is None

    while current != None:

      count = count + 1

      current = current.get_next()

    return count

  '''

  Search for an item in the list. Returns True if found, False otherise.  

  '''

  def search(self,item):

    current = self.head

    found = False

    # As long as the element is not found and we haven't

    # reached the end of the list

    while current != None and not found:

      if current.get_data() == item:

        found = True

      else:

        # go to the next element

        current = current.get_next()

    return found

   

  '''

  Remove the first occurrence of item from the list.  

  '''

  def remove(self, item):

    # keep track of current and previous elements

    current = self.head

    previous = None

    found = False

    # traverse the list

    while current != None and not found:

      # if we have a match, stop

      if current.get_data() == item:

        found = True

      # otherwise advance current and next references

      else:

        previous = current

        current = current.get_next()

      

    # the element to be deleted is the head of the list   

    if found:

      if previous == None:

        self.head = current.get_next()

        # the element to be deleted is not the head

      else:

        previous.set_next(current.get_next())

              
  def print_list(self):
    current = self.head
    # start of list
    print('[',end="")
    while current != None:
      print(current.get_data(),end="")

      current = current.get_next()

      # to avoid printing comma after last element
      if(current!=None):
        print(', ',end="")

    print(']')


def main():

  # create a list and add some elements to it

  aList = UnorderedList()

  print("Adding 3, 5, 8, and 11 to the list.")

  aList.add(3)

  aList.add(5)

  aList.add(8)

  # 11 is the head of the list

  aList.add(11)

   

  print("List size:", aList.size())

  print("Is 5 in the list? ", aList.search(5))

  print("Removing 5 from the list.")

  aList.remove(5)

  print("Is 5 in the list? ", aList.search(5))

  print("List size:", aList.size())

  print("Removing 3 from the list.")

  aList.remove(3)   

  print("List size:", aList.size())

  aList.print_list()
  

if __name__ == "__main__":

  main()