}
public function travel()
{
print "travel start:\n";
$traveled = array();
$curr = $this;
while (true) {
print $curr->val;
// 检查环
if (in_array($curr, $traveled)) {
print " circled-link-list-node";
break;
}
$traveled[] = $curr;
if (empty($curr->next)) {
break;
}
print " => ";
$curr = $curr->next;
}
print "\ntravel end.\n";
}
}
$list = new LinkedList(1, null);
$list->travel();
$list = new LinkedList(1, new LinkedList(2, null));
$list->travel();
$list = new LinkedList(1, new LinkedList(2, null));
$list->next->next = $list;
$list->travel();
