algorithmpool/src/dspool/linked_list/circular_linked_list.js

A pool of algorithms and data-structures for geeks

import {
    defaultEquals
} from '../../utils/util';
import {LinkedList} from './linked_list';
import {
    Node
} from '../models/linked-list-models';

export class CircularLinkedList extends LinkedList {
    constructor(equalsFn = defaultEquals) {
        super(equalsFn);
    }

    push(element) {
        const node = new Node(element);
        let current;
        if (this.head == null) {
            this.head = node;
        } else {
            current = this.getElementAt(this.size() - 1);
            current.next = node;
        }
        // set node.next to head - to have circular list
        node.next = this.head;
        this.count++;
    }

    insert(element, index) {
        if (index >= 0 && index <= this.count) {
            const node = new Node(element);
            let current = this.head;
            if (index === 0) {
                if (this.head == null) {
                    // if no node  in list
                    this.head = node;
                    node.next = this.head;
                } else {
                    node.next = current;
                    current = this.getElementAt(this.size());
                    // update last element
                    this.head = node;
                    current.next = this.head;
                }
            } else {
                const previous = this.getElementAt(index - 1);
                node.next = previous.next;
                previous.next = node;
            }
            this.count++;
            return true;
        }
        return false;
    }

    removeAt(index) {
        if (index >= 0 && index < this.count) {
            let current = this.head;
            if (index === 0) {
                if (this.size() === 1) {
                    this.head = undefined;
                } else {
                    const removed = this.head;
                    current = this.getElementAt(this.size() - 1);
                    this.head = this.head.next;
                    current.next = this.head;
                    current = removed;
                }
            } else {
                // no need to update last element for circular list
                const previous = this.getElementAt(index - 1);
                current = previous.next;
                previous.next = current.next;
            }
            this.count--;
            return current.element;
        }
        return undefined;
    }
}