What makes a Linked List circular?

A Linked List is circular when the last node's "next" pointer points back to the "Head" node instead of being null.

Benefit of Circular Linked Lists?

They allow for continuous traversal of the list from any starting point and are ideal for modeling periodic processes.

Is there a "Null" end in a Circular list?

No, every node points to a valid next node, creating an endless cycle that requires careful termination during traversal.

Circular Linked List

A circular linked list is a linked list whose last node points back to the first node, forming a circle, so there is no NULL at the end.

0 / 8 NODES

READY

List is empty

Insert a value to begin. In a circular list the last node points back at the head, so there is no NULL to stop at.

Value

Intuition

Think of a board game like Monopoly. The spaces form a loop; after the last space, you go back to the start. There is no "end".

Concept

A Circular Linked List is a variation where the last node points back to the first node instead of NULL.

How it Works

No Null: Every node has a successor.
Traversal: Be careful! An infinite loop occurs if you don't stop when you reach the start again.

Step-by-Step Breakdown

Insert at Tail:

Create new node.
Set new node's next to Head.
Find current Tail (node pointing to Head).
Update Tail's next to new node.

When to Use

Round Robin Scheduling: CPU scheduling where processes are given time slots in a circle.
Multi-player Games: Turns pass from player to player in a loop.

When NOT to Use

Simple Lists: If you don't need the circular property, it adds complexity.
Infinite Loops: Risk of bugs if traversal condition is wrong.

How to Identify

Problems dealing with cycles or continuous loops where execution returns to the start.

Sample Problems

Josephus Problem

Eliminate every k-th person in a circle.

Linked List Cycle II

Return the node where the cycle begins.

Applying for software engineering roles? Free, no sign-up:

AI resume checker — match your resume to the job description

Doubly Linked List

Graph Representation

Complexity

Time (Best)

O(1)

Time (Average)

O(n)

Time (Worst)

O(n)

Space

O(n)

Circular Linked List Code

1class Node {
2  constructor(data) {
3    this.data = data;
4    this.next = null;
5  }
6}
7
8class CircularLinkedList {
9  constructor() {
10    this.head = null;
11  }
12
13  insertHead(data) {
14    const newNode = new Node(data);
15    if (!this.head) {
16      this.head = newNode;
17      newNode.next = this.head;
18      return;
19    }
20    let current = this.head;
21    while (current.next !== this.head) {
22      current = current.next;
23    }
24    newNode.next = this.head;
25    this.head = newNode;
26    current.next = this.head;
27  }
28
29  insertTail(data) {
30    const newNode = new Node(data);
31    if (!this.head) {
32      this.head = newNode;
33      newNode.next = this.head;
34      return;
35    }
36    let current = this.head;
37    while (current.next !== this.head) {
38      current = current.next;
39    }
40    current.next = newNode;
41    newNode.next = this.head;
42  }
43
44  deleteHead() {
45    if (!this.head) return;
46    if (this.head.next === this.head) {
47      this.head = null;
48      return;
49    }
50    let current = this.head;
51    while (current.next !== this.head) {
52      current = current.next;
53    }
54    this.head = this.head.next;
55    current.next = this.head;
56  }
57  deleteAt(index) {
58    if (index === 0) return this.deleteHead();
59    let prev = this.head;
60    for (let i = 0; i < index - 1 && prev.next !== this.head; i += 1) prev = prev.next;
61    if (prev.next === this.head) return;
62    prev.next = prev.next.next;
63  }
64}

Related Lessons

Circular Linked List

Intuition

Concept

How it Works

Step-by-Step Breakdown

When to Use

When NOT to Use

How to Identify

Sample Problems

Josephus Problem

Linked List Cycle II

AI resume checker — match your resume to the job description

Frequently Asked Questions

What makes a Linked List circular?

Benefit of Circular Linked Lists?

Is there a "Null" end in a Circular list?