1 
     next指向自己，将自己的next指向null10     #为了获得逆转后的头结点，在最后一个非空节点，即cnode->next == null时，将节点返回11     function reverse_list_r($node) {12         if ($node->next == null) {13             return $node;14         } else {15             $head = reverse_list_r($node->next);16             $node->next->next = $node;17             $node->next = null;18             return $head;19         }20     }21 22     #非递归版本23     #思想是需要保存下三个节点，分别是cnode,next(cnode->next),next2(cnode->next->next)24     #每次要执行的操作只有将next->next指向cnode，然后依次将这三个节点后移，直到next == null25     function reverse_list($head) {26         $cnode = $head;27         $next = $head->next;28         $head->next = null;29         while ($next != null) {30             $next2 = $next->next;31             $next->next = $cnode; 32             $cnode = $next;33             $next = $next2;34         }35 36         return $cnode;37     }38 39     #遍历单链表40     function traverse($head) {41         $cnode = $head;42         while ($cnode != null) {43             echo $cnode->data . " ";44             $cnode = $cnode->next;45         }46         echo "
";47     }48 49     $head = new Node();50     $n1 = new Node();51     $n2 = new Node();52     $n3 = new Node();53     $head->data = 0;54     $n1->data = 1;55     $n2->data = 2;56     $n3->data = 3;57     $head->next = $n1;58     $n1->next = $n2;59     $n2->next = $n3;60     $n3->next = null;61     traverse($head);62 63     $rhead = reverse_list_r($head);64     traverse($rhead);65 66     $rrhead = reverse_list($rhead);67     traverse($rrhead);68 ?>

0 1 2 3 

3 2 1 0 

0 1 2 3