Insert at Middle Specific Position in DSA Python - Build from Scratch

Insert at Middle Specific Position in a Linked List

📖 Scenario: Imagine you are managing a queue of people waiting for a ride. Sometimes, a new person arrives and wants to join the queue at a specific position in the middle, not just at the front or end.

🎯 Goal: You will build a simple linked list and learn how to insert a new node at a specific middle position.

📋 What You'll Learn

Create a linked list with nodes containing values 10, 20, 30, 40, 50

Create a variable called position with value 3

Write code to insert a new node with value 25 at the position in the linked list

Print the linked list after insertion in the format: 10 -> 20 -> 25 -> 30 -> 40 -> 50 -> None

💡 Why This Matters

🌍 Real World

Linked lists are used in real-world applications like music playlists, undo functionality in apps, and managing queues where insertion order matters.

💼 Career

Understanding linked list insertion is fundamental for software developers working with data structures, improving problem-solving and coding interview skills.

1

Create the initial linked list

Create a linked list with nodes containing values 10, 20, 30, 40, 50 using the Node class and link them in order.

DSA Python

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

# Create nodes with values 10, 20, 30, 40, 50 and link them
# Your code here

Hint

Make nodes one by one and connect each node's next to the next node.

2

Set the insertion position

Create a variable called position and set it to 3 to specify where the new node will be inserted.

DSA Python

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

head = Node(10)
second = Node(20)
third = Node(30)
fourth = Node(40)
fifth = Node(50)

head.next = second
second.next = third
third.next = fourth
fourth.next = fifth

# Create variable position and set it to 3
# Your code here

Hint

Just create a variable named position and assign it the value 3.

3

Insert a new node at the specified position

Create a new node with value 25 and insert it at the position in the linked list. Use variables current and count to traverse the list until the node before the insertion point.

DSA Python

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

head = Node(10)
second = Node(20)
third = Node(30)
fourth = Node(40)
fifth = Node(50)

head.next = second
second.next = third
third.next = fourth
fourth.next = fifth

position = 3

# Insert new node with value 25 at position 3
# Your code here

Hint

Traverse the list until just before the position, then link the new node in between.

4

Print the linked list after insertion

Write code to print the linked list starting from head in the format: 10 -> 20 -> 25 -> 30 -> 40 -> 50 -> None.

DSA Python

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

head = Node(10)
second = Node(20)
third = Node(30)
fourth = Node(40)
fifth = Node(50)

head.next = second
second.next = third
third.next = fourth
fourth.next = fifth

position = 3

new_node = Node(25)
current = head
count = 1
while count < position - 1:
    current = current.next
    count += 1
new_node.next = current.next
current.next = new_node

# Print the linked list
# Your code here

Hint

Use a loop to print each node's data followed by '->', and end with 'None'.