Find the Middle Node in a Singly Linked List

Finding the Middle Node

Finding the middle node in a singly linked list involves determining the node that is at the middle position in the list. This can be efficiently achieved using the slow and fast pointer technique.

Step-by-Step Process

Consider a singly linked list with the following structure:

Head -> 1 -> 2 -> 3 -> 4 -> 5 -> None

To find the middle node in this list, follow these steps:

  1. Initialize Two Pointers: Start with two pointers, slow and fast, both set to the head of the list.
  2. Move Pointers: Move the slow pointer one step at a time and the fast pointer two steps at a time.
  3. Check for Middle: When the fast pointer reaches the end of the list (i.e., None), the slow pointer will be at the middle node.
  4. Return the Middle Node: The node where the slow pointer is located is the middle node.

After performing these steps, the slow pointer will point to the middle node of the linked list.

Python Program to Find the Middle Node in a Singly Linked List

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

class SinglyLinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        new_node = Node(data)
        if self.head is None:
            self.head = new_node
            current = self.head
                current =
   = new_node

    def find_middle(self):
        slow = self.head
        fast = self.head
        while fast and
            slow =
            fast =
        return slow

    def traverse(self):
        current = self.head
        while current:
            print(, end=" -> ")
            current =

# Example usage:
linked_list = SinglyLinkedList()
print("Linked list:")
linked_list.traverse()  # Output: 1 -> 2 -> 3 -> 4 -> 5 -> None
middle_node = linked_list.find_middle()
print("Middle node:",  # Output: 3

This Python program defines a singly linked list with methods for appending nodes, finding the middle node using the slow and fast pointer technique, and traversing the list. The find_middle method returns the middle node of the list.