Singly Linked List

A Singly Linked List is a linear data structure made up of nodes, where each node contains data and a reference (pointer) to the next node in the sequence. Unlike arrays, elements are not stored contiguously in memory.

Node Structure

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 not self.head:
            self.head = new_node
            return
        current = self.head
        while current.next:
            current = current.next
        current.next = new_node

    def delete(self, key):
        current = self.head
        prev = None
        while current and current.data != key:
            prev = current
            current = current.next
        if current is None:
            return
        if prev is None:
            self.head = current.next
        else:
            prev.next = current.next

    def traverse(self):
        values = []
        current = self.head
        while current:
            values.append(current.data)
            current = current.next
        return values

Complexity

Advantages & Disadvantages

• Advantage: dynamic size, efficient insertions/deletions at the head.
• Disadvantage: no direct/random access; traversal is required to reach a given position, and extra memory is used for the next pointer.

Applications

• Implementing stacks and queues.
• Dynamic memory allocation systems.
• Building blocks for more advanced structures like hash maps (chaining) and graphs (adjacency lists).