DSA using Python: Assignment-4: Doubly Linked List

In this assignment, we implement a Doubly Linked List (DLL) using Python.  

A DLL is a data structure where each node contains:

- **data** (the value)

- **next** pointer (link to next node)

- **prev** pointer (link to previous node)

It allows traversal in both directions, making insertion and deletion more flexible than a singly linked list.

Assignment-4: Doubly Linked List

### ✅ Task 1: Define Node class

1. Define a class Node to describe a node of a doubly linked list.

### ✅ Task 2: Define DLL class

2. Define a class DLL to implement Doubly Linked List with __init__() method to create and initialise start reference variable.

### ✅ Task 3: is_empty()

3. Define a method is empty() to check if the linked list is empty in DLL class.

### ✅ Task 4: insert_at_start()

4. In class DLL, define a method insert_at_start() to insert an element at the starting of the list.

### ✅ Task 5: insert_at_last()

5. In class DLL, define a method insert_at_last() to insert an element at the end of the list.

### ✅ Task 6: search()

6. In class DLL, define a method search() to find the node with specified element value.

### ✅ Task 7: insert_after()

7. In class DLL, define a method insert_after() to insert a new node after a given node of the list.

### ✅ Task 8: print_all()

8. In class DLL, define a method to print all the elements of the list.

### ✅ Task 9: Iterator

9. In class DLL, implement iterator for DLL to access all the elements of the list in a sequence.

### ✅ Task 10: delete_first()

10. In class DLL, define a method delete_first() to delete first element from the list. 

### ✅ Task 11: delete_last()

11. In class DLL, define a method delete_last() to delete last element from the list.

### ✅ Task 12: delete_item()

12. In class DLL, define a method delete_item() to delete specified element from the list.

A Doubly Linked List gives more flexibility compared to a Singly Linked List as we can traverse in both directions.  

This assignment builds understanding of bidirectional linking and efficient insertion/deletion operations.