Linked Lists

Linked lists are linear data structures where elements are stored in nodes, each pointing to the next node.

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Initial linked list: Head → 10 → 20 → 30 → null

javascript

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// Node Class
class Node {
  constructor(data) {
    this.data = data;
    this.next = null;
  }
}
// Linked List Class
class LinkedList {
  constructor() {
    this.head = null;
    this.size = 0;
  }
  // Add element at end
  append(data) {
    const newNode = new Node(data);
    if (!this.head) {
      this.head = newNode;
    } else {
      let current = this.head;
      while (current.next) {
        current = current.next;
      }
      current.next = newNode;
    }
    this.size++;
  }
  // Add element at beginning
  prepend(data) {
    const newNode = new Node(data);
    newNode.next = this.head;
    this.head = newNode;
    this.size++;
  }
  // Delete element
  delete(data) {
    if (!this.head) return;
    if (this.head.data === data) {
      this.head = this.head.next;
      this.size--;
      return;
    }
    let current = this.head;
    while (current.next && current.next.data !== data) {
      current = current.next;
    }
    if (current.next) {
      current.next = current.next.next;
      this.size--;
    }
  }
  // Time Complexity:
  // Access: O(n)
  // Search: O(n)
  // Insertion: O(1) at head, O(n) at end
  // Deletion: O(n)

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Explanation

Linked lists are dynamic data structures that don't require contiguous memory. Each node contains data and a reference to the next node. Insertion and deletion at the head are O(1), but accessing elements requires traversal (O(n)).

Operations & Complexity

AccessO(n)

Must traverse from head

SearchO(n)

Linear search through nodes

Insertion (head)O(1)

Direct insertion at head

Insertion (end)O(n)

Must traverse to end

DeletionO(n)

Must find node first

Time Complexity