Linked List Notes with Python Programs
1. Introduction
Linked List is a linear data structure where elements (called nodes) are connected using pointers/references.
Each node contains:
- Data → the actual value
- Pointer/Reference → address of the next node
Unlike arrays:
- Memory is not contiguous.
- Size is dynamic.
- Insertions/Deletions are faster (compared to arrays).
2. Types of Linked Lists - Singly Linked List (SLL)
Each node has data + next pointer.
Python Implementation:
class Node:
def __init__(self, data):
self.data = data
self.next = None
class SinglyLinkedList:
def __init__(self):
self.head = None
def display(self):
temp = self.head
while temp:
print(temp.data, end=" -> ")
temp = temp.next
print("None")
def insert_begin(self, data):
new_node = Node(data)
new_node.next = self.head
self.head = new_node
def insert_end(self, data):
new_node = Node(data)
if not self.head:
self.head = new_node
return
temp = self.head
while temp.next:
temp = temp.next
temp.next = new_node
def delete_begin(self):
if self.head:
self.head = self.head.next
def delete_end(self):
if not self.head or not self.head.next:
self.head = None
return
temp = self.head
while temp.next.next:
temp = temp.next
temp.next = None
# Example usage
ll = SinglyLinkedList()
ll.insert_end(10)
ll.insert_end(20)
ll.insert_begin(5)
ll.display()
ll.delete_begin()
ll.display()
ll.delete_end()
ll.display()
