#intuit

DoublyLinkedList.java

public class DoublyLinkedList<T>{
    private class Node{
        T val;
        Node next;
        Node previous;
        
        public Node(T val){
            this.val = val;
        }
    }
    
    private Node head;
    private Node tail;
    private int N; // the size of the list
    
    public void add(T val){
        Node n = new Node(val);
        if(head == null){
            head = n;
            tail = head;
        }else{
            tail.next = n;
            n.previous = tail;
            tail = n;
        }
        N++;
    }
    
    public int size(){
        return N;
    }
}