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""" singly_linked_list.py Contains the implementation of a sinlgy linked list data structure. Author: Ray Wang Created: 12/19/2023 """ # class to represent a node in the linked list class Node: def __init__(self, data): self.data = data self.next = None # class to manage the linked list class SinglyLinkedList: def __init__(self): self.head = None def is_empty(self): """ Checks if the list is empty. Parameters: No parameters. Returns: bool: True if the list is empty, False if not empty. """ return self.head is None def append(self, data): """ Appends a new node with the provided data at the end of the list. Parameters: data: The data to be stored in the node. Returns: Nothing returned. """ new = Node(data) if self.head is None: self.head = new else: current = self.head while current.next: # traverse through the linked list until we reach the last node current = current.next current.next = new # append the new node to the end of the linked list def prepend(self, data): """ Prepends a new node with the provided data at the front of the list. Parameters: data: The data to be stored in the node. Returns: Nothing returned. """ new = Node(data) new.next = self.head self.head = new def delete(self, data): """ Removes the first occurrence of a node with the specified data in the list. Parameters: data: The data to be deleted from the list. Returns: None: None is returned if the list is empty or if no node is found with the specified data. deleted: Returns the deleted node if it is found in the list. """ if self.head is None: return None # returns None if the list is empty current = self.head if current.data == data: # checks if the head node of the linked list contains the specified data and should be removed deleted = current self.head = current.next return deleted while current.next: # traverse through the linked list until we reach the last node if current.next.data == data: # check if the node after the current one contains the specified data and should be removed deleted = current.next current.next = current.next.next # set the current node's next pointer to point towards the node two places after the current node return deleted current = current.next return None # returns None if no node with the specified data is found def __len__(self): """ Returns the length of the linked list Parameters: No parameters. Returns: count: Returns the number of nodes in the linked list. """ current = self.head # set current to the head of the list count = 0 while current: # while current is not None (the list is not empty) count += 1 # increment count variable current = current.next # move current to the next node in the list return count def display(self): """ Displays the entire linked list using print. Parameters: No parameters. Returns: Nothing returned. """ current = self.head while current: # traverses through the list, printing each node as it is visited print(current.data, end=" -> ") current = current.next print("None")

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