DSA — Linked Lists

What is a Linked List?

A linear data structure where elements are stored in nodes, each pointing to the next.

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

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

Operations

Operation	Time Complexity
Insert at head	O(1)
Insert at tail	O(n)
Delete	O(n)
Search	O(n)

Insert Operations

def insert_at_head(self, data):
    new_node = Node(data)
    new_node.next = self.head
    self.head = new_node

def insert_at_tail(self, data):
    new_node = Node(data)
    if not self.head:
        self.head = new_node
        return
    current = self.head
    while current.next:
        current = current.next
    current.next = new_node

Delete Operation

def delete(self, data):
    if not self.head:
        return
    if self.head.data == data:
        self.head = self.head.next
        return
    current = self.head
    while current.next:
        if current.next.data == data:
            current.next = current.next.next
            return
        current = current.next

Traversal

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

Mini Practice

1. Implement a linked list
2. Insert at head and tail
3. Delete a node
4. Traverse and display

Up Next

Continue with Doubly Linked Lists — doubly linked list.