Doubly linked list in Data Structures Theory - Mini Project: Build & Apply

Building a Doubly Linked List

📖 Scenario: Imagine you want to organize a playlist of songs where you can easily move forward and backward through the list. A doubly linked list is a way to connect items so you can go in both directions.

🎯 Goal: You will build the basic structure of a doubly linked list by creating nodes, linking them forward and backward, and completing the list connections.

📋 What You'll Learn

Create a node structure with data, next, and previous links

Set up a doubly linked list with three nodes containing exact values

Link nodes forward and backward correctly

Complete the list by connecting the last node's next to None and the first node's previous to None

💡 Why This Matters

🌍 Real World

Doubly linked lists are used in music players, web browsers, and undo-redo features where moving forward and backward through items is needed.

💼 Career

Understanding doubly linked lists helps in software development roles that require efficient data navigation and manipulation.

1

Create three nodes with data values

Create three variables called node1, node2, and node3. Each should be a dictionary with keys 'data', 'next', and 'prev'. Set the 'data' values to 10, 20, and 30 respectively. Set 'next' and 'prev' to None for all three nodes.

Data Structures Theory

# Create node1, node2, and node3 dictionaries with data, next, and prev keys
# Your code here

Need a hint?

Use dictionaries to represent each node with keys 'data', 'next', and 'prev'. Initialize 'next' and 'prev' as None.

2

Link the nodes forward

Set the 'next' key of node1 to node2, and the 'next' key of node2 to node3. Leave node3's 'next' as None.

Data Structures Theory

node1 = {'data': 10, 'next': None, 'prev': None}
node2 = {'data': 20, 'next': None, 'prev': None}
node3 = {'data': 30, 'next': None, 'prev': None}
# Link node1's next to node2 and node2's next to node3
# Your code here

Need a hint?

Assign the 'next' key of node1 to node2, and the 'next' key of node2 to node3.

3

Link the nodes backward

Set the 'prev' key of node3 to node2, and the 'prev' key of node2 to node1. Leave node1's 'prev' as None.

Data Structures Theory

node1 = {'data': 10, 'next': None, 'prev': None}
node2 = {'data': 20, 'next': None, 'prev': None}
node3 = {'data': 30, 'next': None, 'prev': None}

node1['next'] = node2
node2['next'] = node3
# Link node3's prev to node2 and node2's prev to node1
# Your code here

Need a hint?

Assign the 'prev' key of node3 to node2, and the 'prev' key of node2 to node1.

4

Complete the doubly linked list connections

Ensure that node1's 'prev' is None and node3's 'next' is None to mark the ends of the list.

Data Structures Theory

node1 = {'data': 10, 'next': None, 'prev': None}
node2 = {'data': 20, 'next': None, 'prev': None}
node3 = {'data': 30, 'next': None, 'prev': None}

node1['next'] = node2
node2['next'] = node3

node3['prev'] = node2
node2['prev'] = node1
# Set node1's prev to None and node3's next to None
# Your code here

Need a hint?

Make sure the first node's 'prev' and the last node's 'next' are None to show the list ends.