php 实现链表逆序

<?php
    class Node {
        public $str;        public $next;        function __construct ($str) {
            $this->str = $str;
        }
    }    //创建链表头
    function createList () {
        $head = new Node(null);        return $head;
    }    //向链表$head中插入节点并赋值
    function insertNode ($str, &$head) {
        $node = new Node($str);        $node->next = &$head->next;        $head->next = &$node;
    }    //取出链表的第一个节点，相当于出队
    function outQueue (&$head) {
        $tmp = $head->next;        $head->next = $head->next->next;        $tmp->next = null;        return $tmp;
    }    //将链表$head进行逆序
    function reverse (&$head) {
        $reversed = createList(null);        while (null != $head->next) {
            insertNode(outQueue($head), $reversed);
        }        return $reversed;
    }    $head = createList();
    insertNode(&#39;hello&#39;, $head);
    insertNode(&#39;world&#39;, $head);
    insertNode(&#39;99999999999999&#39;, $head);
    insertNode(&#39;888888888888888&#39;, $head);
    insertNode(&#39;7777777777777&#39;, $head);
    insertNode(&#39;66666666666666&#39;, $head);
    insertNode(&#39;55555555555&#39;, $head);
    insertNode(&#39;444444444444&#39;, $head);
    insertNode(&#39;333333333333&#39;, $head);
    insertNode(&#39;222222222222222&#39;, $head);
    insertNode(&#39;111111111111&#39;, $head);
    insertNode(&#39;000000000000000&#39;, $head);
    print_r($head);    $reversed = reverse($head);    echo "<hr />";
    print_r($reversed);    //上面的方法没有在原链表上操作，不过他创建了一个新链表，
    //虽然逻辑实现显得简单，但是太不专业
    //下面贴出更加专业的逆序代码
    function reverse2 (&$head) {
    $q = $head->next->next;    $head->next->next = null;    while (null != $q) {        $p = $q;        $q = $p->next;        $p->next = $head->next;        $head->next = $p;
    }
    reverse2($head);    echo "<hr />";
    print_r($head);
} ?>