Why Linked List Exists and What Problem It Solves in DSA Python - See It Work

Why Linked List Exists and What Problem It Solves

📖 Scenario: Imagine you have a collection of books that you want to organize on a shelf. Sometimes you want to add a new book in the middle or remove one without moving all the other books. Using a simple list means shifting many books, which takes time. A linked list is like a chain where each book holds a note pointing to the next book, making it easier to add or remove books anywhere.

🎯 Goal: Build a simple linked list in Python to understand why linked lists exist and how they solve the problem of adding and removing items efficiently compared to regular lists.

📋 What You'll Learn

Create a linked list node class with a value and a pointer to the next node

Create a linked list with three nodes connected in order

Add a new node in the middle of the linked list

Print the linked list to show the order of nodes after insertion

💡 Why This Matters

🌍 Real World

Linked lists are used in music players to keep track of songs in order, allowing easy addition or removal of songs without rearranging the entire list.

💼 Career

Understanding linked lists is fundamental for software developers to manage dynamic data efficiently and is often asked in coding interviews.

1

Create the Node class and initial linked list

Create a class called Node with an __init__ method that takes value and sets self.value = value and self.next = None. Then create three nodes named node1, node2, and node3 with values 10, 20, and 30 respectively. Connect them by setting node1.next = node2 and node2.next = node3.

DSA Python

# Create the Node class and three connected nodes
# Your code here

Hint

Define the Node class first. Then create three nodes and link them by setting the next attribute.

2

Add a new node in the middle

Create a new node called node_new with value 15. Insert it between node1 and node2 by setting node_new.next = node2 and node1.next = node_new.

DSA Python

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

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3

# Create node_new with value 15 and insert it between node1 and node2
# Your code here

Hint

Make a new node with value 15. Point its next to node2. Then point node1's next to this new node.

3

Create a function to print the linked list

Define a function called print_linked_list that takes a head node. Use a while loop to traverse nodes starting from head. Print each node's value followed by ' -> ' until the last node, then print 'None'.

DSA Python

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

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3

node_new = Node(15)
node_new.next = node2
node1.next = node_new

# Define print_linked_list function to print all node values
# Your code here

Hint

Start from the head node. Keep moving to the next node until you reach None. Print each value with an arrow.

4

Print the linked list after insertion

Call the function print_linked_list with node1 as the argument to print the linked list values after inserting the new node.

DSA Python

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

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3

node_new = Node(15)
node_new.next = node2
node1.next = node_new

def print_linked_list(head):
    current = head
    while current is not None:
        print(str(current.value) + ' -> ', end='')
        current = current.next
    print('None')

# Call print_linked_list with node1
# Your code here

Hint

Just call print_linked_list(node1) to see the linked list values.