Delete the Head Node of a Singly Linked List

Deleting the Head Node

Deleting the head node of a singly linked list involves updating the head reference to point to the next node in the list. This operation is straightforward and efficient, as it only requires updating one pointer.

---

Step-by-Step Process

Consider a singly linked list with the following structure before deletion:

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

We want to delete the head node (node with value 1). Follow these steps:

1. Check if the List is Empty: If the head is None, the list is already empty, and there is nothing to delete.
2. Update the Head Reference: Update the head reference to point to the next node in the list (node with value 2).
3. Dispose of the Old Head Node: Optionally, set the next reference of the old head node to None to help the garbage collector (if applicable).

After performing these steps, the linked list will have the following structure:

Head -> 2 -> 3 -> 4 -> None

---

Python Program to Delete the Head Node

class Node:
    def __init__(self, data):
        self.data = data
        self.next = 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
        else:
            current = self.head
            while current.next:
                current = current.next
            current.next = new_node

    def delete_head(self):
        if self.head is None:
            print("The list is already empty.")
            return
        self.head = self.head.next

    def traverse(self):
        current = self.head
        while current:
            print(current.data, end=" -> ")
            current = current.next
        print("None")

# Example usage:
linked_list = SinglyLinkedList()
linked_list.append(1)
linked_list.append(2)
linked_list.append(3)
linked_list.append(4)
print("Linked list before deleting head:")
linked_list.traverse()  # Output: 1 -> 2 -> 3 -> 4 -> None
linked_list.delete_head()
print("Linked list after deleting head:")
linked_list.traverse()  # Output: 2 -> 3 -> 4 -> None

This Python program defines a singly linked list with methods for appending nodes, deleting the head node, and traversing the list. The delete_head method updates the head reference to point to the next node in the list, effectively removing the current head node.