diff --git a/Data-Structures/Linked-List/CircularDoublyLinkedList.js b/Data-Structures/Linked-List/CircularDoublyLinkedList.js
new file mode 100644
index 0000000000..72e266decf
--- /dev/null
+++ b/Data-Structures/Linked-List/CircularDoublyLinkedList.js
@@ -0,0 +1,140 @@
+// Explanation:- https://www.javatpoint.com/circular-doubly-linked-list
+
+class Node {
+ /**
+ * Creates a new Node with the given element.
+ * @param {*} element - The element to be stored in the node.
+ */
+ constructor(element) {
+ this.element = element;
+ this.next = null;
+ this.prev = null;
+ }
+}
+
+class CircularDoublyLinkedList {
+ /**
+ * Creates an empty Circular Doubly Linked List.
+ */
+ constructor() {
+ this.length = 0;
+ this.head = null;
+ this.tail = null;
+ }
+
+ /**
+ * Inserts an element at the specified position in the list.
+ * @param {number} position - The position at which to insert the element.
+ * @param {*} element - The element to be inserted.
+ * @returns {boolean} - True if the insertion was successful, false otherwise.
+ */
+ insertAt(position, element) {
+ if (position>= 0 && position <= this.length) { + const node = new Node(element); + let current = this.head; + let previous = null; + let index = 0; + + if (position === 0) { + if (!this.head) { + this.head = node; + this.tail = node; + node.next = node; // Circular reference + node.prev = node; // Circular reference + } else { + node.next = current; + node.prev = this.tail; + this.head = node; + current.prev = node; + this.tail.next = node; + } + } else { + while (index++ < position) { + previous = current; + current = current.next; + } + node.next = current; + node.prev = previous; + previous.next = node; + current.prev = node; + + if (position === this.length) { + this.tail = node; + } + } + + this.length++; + return true; + } else { + return false; + } + } + + /** + * Appends an element to the end of the list. + * @param {*} element - The element to be appended. + */ + append(element) { + return this.insertAt(this.length, element); + } + + /** + * Removes and returns the element at the specified position. + * @param {number} position - The position of the element to be removed. + * @returns {*} - The removed element, or null if the position is invalid. + */ + removeAt(position) { + if (position>= 0 && position < this.length) { + let current = this.head; + let previous = null; + let index = 0; + + if (position === 0) { + this.head = current.next; + this.head.prev = this.tail; + this.tail.next = this.head; + if (this.length === 1) { + this.tail = null; + } + } else { + while (index++ < position) { + previous = current; + current = current.next; + } + previous.next = current.next; + current.next.prev = previous; + + if (position === this.length - 1) { + this.tail = previous; + } + } + + this.length--; + return current.element; + } else { + return null; + } + } + + /** + * Iterator over the elements in the list. + */ + *elements() { + let currentNode = this.head; + if (!currentNode) return; + do { + yield currentNode.element; + currentNode = currentNode.next; + } while (currentNode !== this.head); + } + + /** + * Checks if the list is empty. + * @returns {boolean} - True if the list is empty, false otherwise. + */ + isEmpty() { + return this.length === 0; + } +} + +export { CircularDoublyLinkedList }; diff --git a/Data-Structures/Linked-List/test/CircularDoublyLinkedList.test.js b/Data-Structures/Linked-List/test/CircularDoublyLinkedList.test.js new file mode 100644 index 0000000000..f2ade52984 --- /dev/null +++ b/Data-Structures/Linked-List/test/CircularDoublyLinkedList.test.js @@ -0,0 +1,58 @@ +import { CircularDoublyLinkedList } from '../CircularDoublyLinkedList'; + +describe('CircularDoublyLinkedList', () => {
+ /**
+ * Creates a new CircularDoublyLinkedList and appends elements to it.
+ * @param {Array} elements - The elements to append.
+ * @returns {CircularDoublyLinkedList} - The created list.
+ */
+ function createAndAppend(elements) {
+ const list = new CircularDoublyLinkedList();
+ elements.forEach((element) => list.append(element));
+ return list;
+ }
+
+ const expectList = (list, expected) => expect([...list.elements()]).toEqual(expected);
+
+ it('append', () => {
+ const list = createAndAppend([1]);
+
+ expectList(list, [1]);
+
+ list.append(2);
+ expectList(list, [1, 2]);
+ });
+
+ it('insertAt', () => {
+ const list = createAndAppend([1]);
+
+ list.insertAt(0, 20);
+ expectList(list, [20, 1]);
+
+ list.insertAt(1, 30);
+ expectList(list, [20, 30, 1]);
+ });
+
+ it('removeAt', () => {
+ const list = createAndAppend([10, 40, 30]);
+
+ list.removeAt(0);
+ expectList(list, [40, 30]);
+
+ list.removeAt(1);
+ expectList(list, [40]);
+ });
+
+ it('elements', () => {
+ const list = createAndAppend([10, 20, 30]);
+ expect([...list.elements()]).toEqual([10, 20, 30]);
+ });
+
+ it('isEmpty', () => {
+ const emptyList = new CircularDoublyLinkedList();
+ expect(emptyList.isEmpty()).toEqual(true);
+
+ const nonEmptyList = createAndAppend(['Hello']);
+ expect(nonEmptyList.isEmpty()).toEqual(false);
+ });
+});
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