php 单向链表反转 reverse (没有空的头结点)

<?php/** * Created by PhpStorm. * User: Mch * Date: 8/11/18 * Time: 00:25 */class Node { ???public $value; ???public $next; ???public function __construct($data) { ???????$this->value = $data; ???????$this->next = null; ???}} class LinkedList implements Iterator, Countable { ???private $head; ???private $cur; ????public function __construct() { ???????$this->head = $this->cur = null; ???} ????public function isEmpty() { ???????return is_null($this->head); ???} ????public function count() { ???????$p = $this->head; ???????$count = 0; ???????while ($p !== null) { ???????????$p = $p->next; ???????????$count++; ???????} ???????return $count; ???} ???public function current() { ???????if ($this->isEmpty()) { ???????????return null; ???????} ???????return $this->cur->value; ???} ???public function next() { ???????if (is_null($this->cur)) { ???????????return null; ???????} ???????$this->cur = $this->cur->next; ???} ???public function rewind() { ???????$this->cur = $this->head; ???} ????public function valid() { ???????return !is_null($this->cur); ???} ???public function key() { ???????$p = $this->head; ???????$key = 0; ???????while ($p !== $this->cur) { ???????????$p = $p->next; ???????????$key++; ???????} ???????return $key; ???} ???public function push($value) { ???????if ($this->isEmpty()) { ???????????$this->head = new Node($value); ???????????$this->cur = $this->head; ???????} else { ???????????$this->cur = $this->head; ???????????while ($this->cur->next !== null) { ???????????????$this->cur = $this->cur->next; ???????????} ???????????$this->cur->next = new Node($value); ???????} ???????return $this; ???} ????public function forEach(callable $callback, mixed $userdata = null) { ???????$this->rewind(); ???????while($this->valid()) { ???????????call_user_func($callback, $this->current(), $this->key(), $userdata); ???????????$this->next(); ???????} ???} ????public function reverse() { ???????if ($this->isEmpty()) ???????????return; ???????if ($this->count() < 2) ???????????return; ???????$prev = null; ???????$cur = $this->head; ???????while ($cur) { ???????????// save next ???????????$next = $cur->next; ???????????// move cur to head ???????????$this->head = $cur; ???????????$cur->next = $prev; ???????????// iterate ???????????$prev = $cur; ???????????$cur = $next; ???????} ???} }

$list = new LinkedList(); for ($i = 65; $i < 91; $i++) { ???$list->push(chr($i));} $list->forEach(function($value, $index) { ???printf("[%d] => %s<br />", $index, $value);});echo ‘-------------------<br />‘;$list->reverse();$list->forEach(function($value, $index) { ???printf("[%d] => %s<br />", $index, $value);});