import java.util.Iterator;
import java.util.NoSuchElementException;

/**Realization of a set by means of a singly linked list
*/
public class NodeSet<E> implements Set<E> {
	private Node<E> head;
	private Node<E> tail;
	private int size;
	
	
	
	/**Creates an empty set*/
	public NodeSet(){
		head=null;
		tail=null;
		size=0;
	}
	
	
	
	public Node<E> getHead() {
		return head;
	}


   public void setHead(Node<E> h) {
		this.head = h;
	}




	public Node getTail() {
		return tail;
	}



   public void setTail(Node<E> t) {
		this.tail = t;
	}



    public int size() {
       return size;
	}
	
	

	/**Adds the specified element to this set if not already present */
	public boolean add(E e) {
		boolean toAdd=false;
		if (!contains(e)){
			toAdd=true;
		    Node<E> temp=new Node<E>(e,null);
		    if(isEmpty()){head=temp;tail=temp;}
		    else tail.setNext(temp);
		    tail=temp;
		    size++;
		}
		return toAdd;
	}
	
	/**Removes all of the elements from this set*/
	public void clear(){
		head=null;
		tail=null;
		size=0;
	}
	
	/**Returns true if this collection contains the specified element*/
	public boolean contains(E e){
		for(E eTemp:this) if(eTemp.equals(e)) return true;
		return false;
	}
	
	
	
	/**Removes the specified element from this set, if it is present*/
	public boolean remove(E e){
		if(isEmpty()) return false;
		Node<E> temp=head;
		Node<E> prev=null;
		boolean found=false;
		while((temp!=null)&&(found==false)){
			if(temp.getElement().equals(e)){
				found=true;
				if (temp==head) head=temp.getNext();
				else{
					prev.setNext(temp.getNext());
					temp=null;
				}
				size--;
			}
			else{prev=temp;temp=temp.getNext();}
		}
		return found;
	}

	
	/**Returns true if the set contains no elements*/
	public boolean isEmpty() {
		return size==0;
	}
	
	
	
	public Iterator<E> iterator()
	{NodeSetIterator tempIterator=new NodeSetIterator();
	 return (Iterator<E>) tempIterator;}
	
	private class NodeSetIterator implements Iterator<E>{
		private Node<E> current=head;
		
		/**Returns true if the iteration has more elements*/
		public boolean hasNext()
		{return current!=null;}
		
		public E next(){
			if(!hasNext())
				throw new NoSuchElementException();
			E nextItem=current.getElement();
			current=current.getNext();
			return nextItem;
		}
		
		/**Removes from the underlying collection the last element returned by the iterator*/
		public void remove(){};
			// not implemented
		}
		
	
	
	 public String toString(){
		String s="";
		int count=0;
		for(E sTemp:this) {s+=" "+sTemp;
		count++;
		if (count==20){s+="\n";count=0;}//to add line breaks
		}
		return s;
		 }

}