php 实现链表逆序

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<?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);
} ?>

输出结果：
逆序前的链表：
Node Object ( [str] => [next] => Node Object ( [str] => 000000000000000 [next] => Node Object ( [str] => 111111111111 [next] => Node Object ( [str] => 222222222222222 [next] => Node Object ( [str] => 333333333333 [next] => Node Object ( [str] => 444444444444 [next] => Node Object ( [str] => 55555555555 [next] => Node Object ( [str] => 66666666666666 [next] => Node Object ( [str] => 7777777777777 [next] => Node Object ( [str] => 888888888888888 [next] => Node Object ( [str] => 99999999999999 [next] => Node Object ( [str] => world [next] => Node Object ( [str] => hello [next] => ) ) ) ) ) ) ) ) ) ) ) ) )

逆序后的链表：
Node Object ( [str] => [next] => Node Object ( [str] => Node Object ( [str] => hello [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => world [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 99999999999999 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 888888888888888 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 7777777777777 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 66666666666666 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 55555555555 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 444444444444 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 333333333333 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 222222222222222 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 111111111111 [next] => ) [next] => Node Object ( [str] => Node Object ( [str] => 000000000000000 [next] => ) [next] => ) ) ) ) ) ) ) ) ) ) ) ) )

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