public class ILinkedList {

	private Node head ;
    private Node tail ;
    private int size ;

    public Node getHead() {
        return head;
    }
    public void setHead(Node head) {
        this.head = head;
    }
    public Node getTail() {
        return tail;
    }
    public void setTail(Node tail) {
        this.tail = tail;
    }
    public int getSize() {
        return size;
    }
    public void setSize(int size) {
        this.size = size;
    }

    public void add (int index , Term a)
    {
        Node n = new Node (a);
        Node curr = head ;
        if( index > size - 1 || index < 0)
        {
            return;
        }
        if ( head == null )
        {
            head = n ;
            tail = n ;
        }
        else if (index == 0)
        {

            n.setNext(head);
            head = n;
        }
        else if (index == size )
        {
            add( a );
        }
        else
        {
            for( int i = 0 ; i < index - 1 ; i++ )
            {
                curr = curr.getNext();
            }

            n.setNext(curr.getNext());

            curr.setNext(n);
        }
        size++;
    }
    public void add(Term a)
    {
        Node n = new Node (a) ;
        if( head == null )
        {
            head = n ;
        }
        else
        {
            tail.setNext(n);

        }
        tail = n ;
        size++ ;
    }
    public Term get ( int index )
    {
        if( index < 0 || index > size - 1 )
        {
            return null ;
        }
        Node curr = head ;
        if(head == null )
        {
            return null ;
        }
        for(int i = 0 ; i < index ; i++ )
        {
            curr = curr.getNext();
        }
        return curr.getX();
    }
    public void set( int index , Term a )
    {
        if( index > size - 1 || index < 0)
        {
            return;
        }
        Node curr = head ;
        for(int i = 0 ; i < index ; i++ )
        {
            curr = curr.getNext();
        }
        curr.setX(a);
    }
    public void clear ( )
    {
        head = null ;
        tail = null ;
        size = 0 ;
    }
    public boolean isEmpty ()
    {
        return head == null ;
    }
    public void remove (int index)
    {
        if( head == null || index > size - 1 || index < 0 )
        {
            return;
        }
        if( head == tail )
        {
            head = null ;
            tail = null ;
        }
        else if( index == 0 )
        {
            Node removed = head ;
            head = head.getNext();
            removed.setNext(null);
        }
        else
        {
            Node curr = head;
            for(int i = 0 ; i < index-1 ; i++ )
            {
                curr = curr.getNext();
            }
           Node removed=curr.getNext();
            curr.setNext(removed.getNext());
            removed.setNext(null);
        }
        size--;
    }
    public ILinkedList sublist ( int fromIndex , int toIndex )
    {
        if ( head == null || fromIndex < 0 || fromIndex > size - 1 || toIndex < 0  || toIndex > size - 1 || fromIndex > toIndex)
        {
            return null ;
        }
        int sizeSublist = ( toIndex - fromIndex ) + 1 ;
        ILinkedList sublist = new ILinkedList() ;
        Node curr = head ;
        for( int i = 0 ; i < size  ; i++)
        {
            if( IsIncluded(i, fromIndex, toIndex) )
            {
                sublist.add(curr.getX());
            }
            curr = curr.getNext() ;
        }
        sublist.setSize(sizeSublist);
        return sublist ;
    }
    public boolean IsIncluded (int index , int fromIndex , int toIndex)
    {
        return index >= fromIndex && index <= toIndex ;
    }
    public boolean contains ( Term a )
    {
        if ( head == null )
        {
            return false ;
        }
        Node curr = head ;
        while (curr != null )
        {
            if( curr.getX().equals(a) )
            {
                return true;
            }
            curr = curr.getNext() ;
        }
        return false ;
    }
}