boolean dejaDansListe(Position pos, Hashtable<Position, Noeud> liste)
	{
	    Enumeration<Position> keys = liste.keys();
	    while (keys.hasMoreElements())
	    {
	    	Position pCourant = keys.nextElement();
	    	if (pCourant.getX() == pos.getX() && pCourant.getY() == pos.getY())
	    	{
	    		return true;
	    	}
	    }
	    return false;
	}