Method addAtTail

javascript/0707-design-linked-list.js:35–44

(val)

    }

    addAtTail(val) {
        if (this.head === null) {
            this.head = new Node(val);
            this.tail = this.head;
        } else {
            this.tail.next = new Node(val);
            this.tail.next.prev = this.tail;
            this.tail = this.tail.next;
        }
    }

    addAtIndex(index, val) {
        if (index === 0) this.addAtHead(val);