Why Doubly Linked List Over Singly Linked List in DSA Python - See It Work

Why Doubly Linked List Over Singly Linked List

📖 Scenario: Imagine you are managing a playlist of songs on your music app. You want to move forward and backward through songs easily.

🎯 Goal: You will build a simple doubly linked list to understand why it is better than a singly linked list for moving both forward and backward.

📋 What You'll Learn

Create a doubly linked list with three nodes containing the songs 'Song1', 'Song2', and 'Song3'.

Add a variable to keep track of the current song node.

Write code to move forward to the next song and backward to the previous song.

Print the current song after moving forward and backward.

💡 Why This Matters

🌍 Real World

Music players, web browsers (back and forward buttons), and undo-redo features use doubly linked lists to move easily in both directions.

💼 Career

Understanding doubly linked lists helps in jobs involving data structure design, software development, and optimizing navigation features.

1

Create a doubly linked list with three songs

Create a class called Node with attributes data, prev, and next. Then create three nodes with data 'Song1', 'Song2', and 'Song3'. Link them so that node1.next = node2, node2.prev = node1, node2.next = node3, and node3.prev = node2.

DSA Python

# Define Node class and create three linked nodes
# Your code here

Hint

Remember, each node needs to know its previous and next node to move both ways.

2

Add a variable to track the current song

Create a variable called current and set it to node1 to start at the first song.

DSA Python

class Node:
    def __init__(self, data):
        self.data = data
        self.prev = None
        self.next = None

node1 = Node('Song1')
node2 = Node('Song2')
node3 = Node('Song3')

node1.next = node2
node2.prev = node1
node2.next = node3
node3.prev = node2

# Set current to node1
# Your code here

Hint

This variable will help us know which song is playing now.

3

Move forward and backward through the playlist

Write code to move current to the next song using current = current.next and then move back to the previous song using current = current.prev.

DSA Python

class Node:
    def __init__(self, data):
        self.data = data
        self.prev = None
        self.next = None

node1 = Node('Song1')
node2 = Node('Song2')
node3 = Node('Song3')

node1.next = node2
node2.prev = node1
node2.next = node3
node3.prev = node2

current = node1

# Move current to next song
# Move current back to previous song
# Your code here

Hint

Use the next and prev links to move forward and backward.

4

Print the current song after moving forward and backward

Write two print statements: one to print current.data after moving forward, and one to print current.data after moving backward.

DSA Python

class Node:
    def __init__(self, data):
        self.data = data
        self.prev = None
        self.next = None

node1 = Node('Song1')
node2 = Node('Song2')
node3 = Node('Song3')

node1.next = node2
node2.prev = node1
node2.next = node3
node3.prev = node2

current = node1

current = current.next
# Print current song after moving forward

current = current.prev
# Print current song after moving backward

Hint

Print the data of the current node after each move.