linked_list_manager

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Filename: linked_list_manager.py
# Version: 1.0.0
# Author: Jeoi Reqi

"""
Description:
    This script provides classes for implementing singly linked lists and doubly linked lists in Python.
    It includes functionalities to insert nodes at the front and end of the lists, remove nodes from the front and end,
    and print the contents of the lists.

Requirements:
    - Python 3.x

Functions:
    - ListNode.__init__(self, val):
        Initializes a node with a given value.
    - DoublyLinkedList.__init__(self):
        Initializes a doubly linked list.
    - DoublyLinkedList.insertFront(self, val):
        Inserts a node with the given value at the front of the doubly linked list.
    - DoublyLinkedList.insertEnd(self, val):
        Inserts a node with the given value at the end of the doubly linked list.
    - DoublyLinkedList.removeFront(self):
        Removes the node at the front of the doubly linked list.
    - DoublyLinkedList.removeEnd(self):
        Removes the node at the end of the doubly linked list.
    - DoublyLinkedList.print_list(self):
        Prints the contents of the doubly linked list in reverse order.
    - LinkedList.__init__(self):
        Initializes a singly linked list.
    - LinkedList.insertEnd(self, val):
        Inserts a node with the given value at the end of the singly linked list.
    - LinkedList.print_list(self):
        Prints the contents of the singly linked list.

Example Output:

    Choose an option:

    1: Linked List
    2: Doubly-Linked List
    0: Exit

    Enter your choice: 1

    Enter a string value to insert: Single
    Single  ->
    Choose an option:

    1: Linked List
    2: Doubly-Linked List
    0: Exit

    Enter your choice: 2

    Enter a string value to insert: Double
    Single  -> Double  ->

Usage:
    - Instantiate LinkedList or DoublyLinkedList objects.
    - Use insertEnd() to insert nodes into the linked lists.
    - Use print_list() to print the contents of the linked lists.
    - Run the script to interactively choose options for adding elements to the lists or exiting the program.
"""

class ListNode:
    """Represents a node in a linked list."""
    def __init__(self, val):
        """Initializes a node with a given value."""
        self.val = val
        self.next = None
        self.prev = None

class DoublyLinkedList:
    """Represents a doubly linked list."""
    def __init__(self):
        """Initializes a doubly linked list."""
        self.head = ListNode(None)
        self.tail = ListNode(None)
        self.head.next = self.tail
        self.tail.prev = self.head

    def insertFront(self, val):
        """Inserts a node with the given value at the front of the doubly linked list."""
        new_node = ListNode(val)
        new_node.prev = self.head
        new_node.next = self.head.next
        self.head.next.prev = new_node
        self.head.next = new_node

    def insertEnd(self, val):
        """Inserts a node with the given value at the end of the doubly linked list."""
        new_node = ListNode(val)
        new_node.next = self.tail
        new_node.prev = self.tail.prev
        self.tail.prev.next = new_node
        self.tail.prev = new_node

    def removeFront(self):
        """Removes the node at the front of the doubly linked list."""
        first_node = self.head.next
        first_node.next.prev = self.head
        self.head.next = first_node.next

    def removeEnd(self):
        """Removes the node at the end of the doubly linked list."""
        last_node = self.tail.prev
        last_node.prev.next = self.tail
        self.tail.prev = last_node.prev

    def print_list(self):
        """Prints the contents of the doubly linked list in reverse order."""
        current_node = self.tail.prev
        while current_node != self.head:
            print(current_node.val, " -> ", end="")
            current_node = current_node.prev
        print()

class LinkedList:
    """Represents a singly linked list."""
    def __init__(self):
        """Initializes a singly linked list."""
        self.head = None

    def insertEnd(self, val):
        """Inserts a node with the given value at the end of the singly linked list."""
        new_node = ListNode(val)
        if self.head is None:
            self.head = new_node
        else:
            current = self.head
            while current.next:
                current = current.next
            current.next = new_node

    def print_list(self):
        """Prints the contents of the singly linked list."""
        current = self.head
        while current:
            print(current.val, " -> ", end="")
            current = current.next
        print()

def main():
    """Main function for interactive usage."""
    choice = None
    linked_list = LinkedList()
    doubly_linked_list = DoublyLinkedList()
    while choice != '0':
        print("Choose an option:\n")
        print("1: Linked List")
        print("2: Doubly-Linked List")
        print("0: Exit")
        choice = input("\nEnter your choice: ")

        if choice == '1':
            val = input("\nEnter a string value to insert: ")
            linked_list.insertEnd(val)
            doubly_linked_list.insertFront(val)
            linked_list.print_list()
        elif choice == '2':
            val = input("\nEnter a string value to insert: ")
            doubly_linked_list.insertFront(val)
            linked_list.insertEnd(val)
            doubly_linked_list.print_list()
        elif choice == '0':
            print("\nExiting Program...   GoodBye!\n")
        else:
            print("\nInvalid choice! Please enter a valid option.\n")

if __name__ == "__main__":
    main()