php - 将一系列父子关系转换为分层树?

我有一堆名字 - 父母对,我希望尽可能少地转化为树状结构。 例如,这些可能是配对:

Child : Parent
    H : G
    F : G
    G : D
    E : D
    A : E
    B : C
    C : E
    D : NULL

需要转换为(a)分层树:

D
├── E
│   ├── A
│   │   └── B
│   └── C   
└── G
    ├── F
    └── H

我想要的最终结果是一组嵌套的<ul>元素,每个元素包含<li>的子名称。

配对中没有不一致(孩子是自己的父母,父母是孩子的孩子等),所以可能会做出一堆优化。

在PHP中,我如何从包含child =&gt;父对的数组转到一组嵌套<ul>s?

我有一种感觉,涉及递归,但我不太清醒,无法思考它。

Eric asked 2019-08-13T00:53:22Z
8个解决方案
120 votes

这需要一个非常基本的递归函数来将子/父对解析为树结构,另一个递归函数将其打印出来。 只有一个功能就足够了,但为了清楚起见,这里有两个功能(在这个答案的最后可以找到组合功能)。

首先初始化子/父对的数组:

$tree = array(
    'H' => 'G',
    'F' => 'G',
    'G' => 'D',
    'E' => 'D',
    'A' => 'E',
    'B' => 'C',
    'C' => 'E',
    'D' => null
);

然后将该数组解析为分层树结构的函数:

function parseTree($tree, $root = null) {
    $return = array();
    # Traverse the tree and search for direct children of the root
    foreach($tree as $child => $parent) {
        # A direct child is found
        if($parent == $root) {
            # Remove item from tree (we don't need to traverse this again)
            unset($tree[$child]);
            # Append the child into result array and parse its children
            $return[] = array(
                'name' => $child,
                'children' => parseTree($tree, $child)
            );
        }
    }
    return empty($return) ? null : $return;    
}

并且遍历该树以打印出无序列表的函数:

function printTree($tree) {
    if(!is_null($tree) && count($tree) > 0) {
        echo '<ul>';
        foreach($tree as $node) {
            echo '<li>'.$node['name'];
            printTree($node['children']);
            echo '</li>';
        }
        echo '</ul>';
    }
}

而实际用途:

$result = parseTree($tree);
printTree($result);

这是$result的内容:

Array(
    [0] => Array(
        [name] => D
        [children] => Array(
            [0] => Array(
                [name] => G
                [children] => Array(
                    [0] => Array(
                        [name] => H
                        [children] => NULL
                    )
                    [1] => Array(
                        [name] => F
                        [children] => NULL
                    )
                )
            )
            [1] => Array(
                [name] => E
                [children] => Array(
                    [0] => Array(
                        [name] => A
                        [children] => NULL
                    )
                    [1] => Array(
                        [name] => C
                        [children] => Array(
                            [0] => Array(
                                [name] => B
                                [children] => NULL
                            )
                        )
                    )
                )
            )
        )
    )
)

如果您想要更高效率,可以将这些功能合并为一个并减少迭代次数:

function parseAndPrintTree($root, $tree) {
    $return = array();
    if(!is_null($tree) && count($tree) > 0) {
        echo '<ul>';
        foreach($tree as $child => $parent) {
            if($parent == $root) {                    
                unset($tree[$child]);
                echo '<li>'.$child;
                parseAndPrintTree($child, $tree);
                echo '</li>';
            }
        }
        echo '</ul>';
    }
}

您只能在数据集上保存8次迭代,但是在较大的集合上,它可能会有所不同。

Tatu Ulmanen answered 2019-08-13T00:54:26Z
53 votes

还有另一个创建树的函数(不涉及递归,而是使用引用):

$array = array('H' => 'G', 'F' => 'G', ..., 'D' => null);

function to_tree($array)
{
    $flat = array();
    $tree = array();

    foreach ($array as $child => $parent) {
        if (!isset($flat[$child])) {
            $flat[$child] = array();
        }
        if (!empty($parent)) {
            $flat[$parent][$child] =& $flat[$child];
        } else {
            $tree[$child] =& $flat[$child];
        }
    }

    return $tree;
}

返回一个像这样的分层数组:

Array(
    [D] => Array(
        [G] => Array(
            [H] => Array()
            [F] => Array()
        )
        ...
    )
)

可以使用递归函数轻松打印为HTML列表。

Alexander Konstantinov answered 2019-08-13T00:55:04Z
28 votes

另一种更简化的方法是将RecursiveIteratorIterator中的扁平结构转换为层次结构。 只需要一个临时数组来公开它:

// add children to parents
$flat = array(); # temporary array
foreach ($tree as $name => $parent)
{
    $flat[$name]['name'] = $name; # self
    if (NULL === $parent)
    {
        # no parent, is root element, assign it to $tree
        $tree = &$flat[$name]; 
    }
    else
    {
        # has parent, add self as child    
        $flat[$parent]['children'][] = &$flat[$name];
    }
}
unset($flat);

这就是将层次结构变为多维数组的全部内容:

Array
(
    [children] => Array
        (
            [0] => Array
                (
                    [children] => Array
                        (
                            [0] => Array
                                (
                                    [name] => H
                                )

                            [1] => Array
                                (
                                    [name] => F
                                )

                        )

                    [name] => G
                )

            [1] => Array
                (
                    [name] => E
                    [children] => Array
                        (
                            [0] => Array
                                (
                                    [name] => A
                                )

                            [1] => Array
                                (
                                    [children] => Array
                                        (
                                            [0] => Array
                                                (
                                                    [name] => B
                                                )

                                        )

                                    [name] => C
                                )

                        )

                )

        )

    [name] => D
)

如果你想避免递归,输出就不那么简单了(对于大型结构来说可能是一种负担)。

我一直想解决UL / LI&#34;困境&#34; 用于输出数组。 困境是,每个项目都不知道孩子是否会跟进或需要关闭多少先前元素。 在另一个答案中,我已经通过使用RecursiveIteratorIterator并寻找RecursiveIterator以及我自己编写的TreeNode提供的其他元信息解决了这个问题:将嵌套集模型转换为RecursiveIterator但隐藏“已关闭”子树。 答案也表明,使用迭代器,你会非常灵活。

然而,这是一个预先排序的列表,因此不适合您的示例。 另外,我一直想为一种标准树结构和HTML的RecursiveIteratorTreeNode元素解决这个问题。

我提出的基本概念如下:

  1. RecursiveIterator - 将每个元素抽象为一个简单的RecursiveIterator类型,它可以提供它的值(例如TreeNode)以及它是否有子节点。
  2. RecursiveIterator - 一个RecursiveIterator,能够迭代这些TreeNode的集合(数组)。这很简单,因为ListDecorator类型已经知道它是否有子节点和哪些。
  3. RecursiveIterator - 一个RecursiveIterator,当递归迭代任何类型的TreeNode时,它具有所需的所有事件:
    • RecursiveIterator/TreeNode - 主列表的开头和结尾。
    • RecursiveIterator/TreeNode - 每个元素的开头和结尾。
    • RecursiveIterator/TreeNode - 每个子项列表的开头和结尾。ListDecorator仅以函数调用的形式提供这些事件。 子列表,因为它通常是addDecorator列表,在其父级<li>元素内打开和关闭。 因此,endElement事件在根据endChildren事件后被触发。 这可以更改或可配置以扩大此类的使用范围。 事件作为函数调用分发给装饰器对象,然后将事物分开。
  4. RecursiveIterator - A&#34; decorator&#34; 这个类只是RecursiveIterator事件的接收者。

我从主输出逻辑开始。 采用现在分层的RecursiveIterator数组,最终代码如下所示:

$root = new TreeNode($tree);
$it = new TreeNodesIterator(array($root));
$rit = new RecursiveListIterator($it);
$decor = new ListDecorator($rit);
$rit->addDecorator($decor);

foreach($rit as $item)
{
    $inset = $decor->inset(1);
    printf("%s%s\n", $inset, $item->getName());
}

首先让我们看看RecursiveIterator,它简单地包装了TreeNodeListDecorator元素,并决定如何输出列表结构:

class ListDecorator
{
    private $iterator;
    public function __construct(RecursiveListIterator $iterator)
    {
        $this->iterator = $iterator;
    }
    public function inset($add = 0)
    {
        return str_repeat('  ', $this->iterator->getDepth()*2+$add);
    }

构造函数采用它正在处理的列表迭代器。 RecursiveIterator只是一个帮助函数,可以很好地缩进输出。 其余的只是每个事件的输出函数:

    public function beginElement()
    {
        printf("%s<li>\n", $this->inset());
    }
    public function endElement()
    {
        printf("%s</li>\n", $this->inset());
    }
    public function beginChildren()
    {
        printf("%s<ul>\n", $this->inset(-1));
    }
    public function endChildren()
    {
        printf("%s</ul>\n", $this->inset(-1));
    }
    public function beginIteration()
    {
        printf("%s<ul>\n", $this->inset());
    }
    public function endIteration()
    {
        printf("%s</ul>\n", $this->inset());
    }
}

考虑到这些输出功能,这又是主要的输出总结/循环,我一步一步地完成它:

$root = new TreeNode($tree);

创建根RecursiveIterator,它将用于开始迭代:

$it = new TreeNodesIterator(array($root));

RecursiveIteratorTreeNode,它允许在单个ListDecorator节点上进行递归迭代。 它作为一个数组传递,因为该类需要迭代一些东西并允许重复使用一组子项,这也是一个addDecorator元素的数组。

$rit = new RecursiveListIterator($it);

这个RecursiveIteratorTreeNode,提供上述事件。 要使用它,只需要提供ListDecorator(上面的类)并分配addDecorator

$decor = new ListDecorator($rit);
$rit->addDecorator($decor);

然后一切都设置为RecursiveIterator并输出每个节点:

foreach($rit as $item)
{
    $inset = $decor->inset(1);
    printf("%s%s\n", $inset, $item->getName());
}

如此示例所示,整个输出逻辑封装在RecursiveIterator类和此单个TreeNode中。整个递归遍历已完全封装到提供堆栈过程的SPL递归迭代器中,这意味着内部不会执行递归函数调用。

基于事件RecursiveIterator允许您专门修改输出并为同一数据结构提供多种类型的列表。 甚至可以在阵列数据封装到TreeNode时更改输入。

完整的代码示例:

<?php
namespace My;

$tree = array('H' => 'G', 'F' => 'G', 'G' => 'D', 'E' => 'D', 'A' => 'E', 'B' => 'C', 'C' => 'E', 'D' => null);

// add children to parents
$flat = array(); # temporary array
foreach ($tree as $name => $parent)
{
    $flat[$name]['name'] = $name; # self
    if (NULL === $parent)
    {
        # no parent, is root element, assign it to $tree
        $tree = &$flat[$name];
    }
    else
    {
        # has parent, add self as child    
        $flat[$parent]['children'][] = &$flat[$name];
    }
}
unset($flat);

class TreeNode
{
    protected $data;
    public function __construct(array $element)
    {
        if (!isset($element['name']))
            throw new InvalidArgumentException('Element has no name.');

        if (isset($element['children']) && !is_array($element['children']))
            throw new InvalidArgumentException('Element has invalid children.');

        $this->data = $element;
    }
    public function getName()
    {
         return $this->data['name'];
    }
    public function hasChildren()
    {
        return isset($this->data['children']) && count($this->data['children']);
    }
    /**
     * @return array of child TreeNode elements 
     */
    public function getChildren()
    {        
        $children = $this->hasChildren() ? $this->data['children'] : array();
        $class = get_called_class();
        foreach($children as &$element)
        {
            $element = new $class($element);
        }
        unset($element);        
        return $children;
    }
}

class TreeNodesIterator implements \RecursiveIterator
{
    private $nodes;
    public function __construct(array $nodes)
    {
        $this->nodes = new \ArrayIterator($nodes);
    }
    public function  getInnerIterator()
    {
        return $this->nodes;
    }
    public function getChildren()
    {
        return new TreeNodesIterator($this->nodes->current()->getChildren());
    }
    public function hasChildren()
    {
        return $this->nodes->current()->hasChildren();
    }
    public function rewind()
    {
        $this->nodes->rewind();
    }
    public function valid()
    {
        return $this->nodes->valid();
    }   
    public function current()
    {
        return $this->nodes->current();
    }
    public function key()
    {
        return $this->nodes->key();
    }
    public function next()
    {
        return $this->nodes->next();
    }
}

class RecursiveListIterator extends \RecursiveIteratorIterator
{
    private $elements;
    /**
     * @var ListDecorator
     */
    private $decorator;
    public function addDecorator(ListDecorator $decorator)
    {
        $this->decorator = $decorator;
    }
    public function __construct($iterator, $mode = \RecursiveIteratorIterator::SELF_FIRST, $flags = 0)
    {
        parent::__construct($iterator, $mode, $flags);
    }
    private function event($name)
    {
        // event debug code: printf("--- %'.-20s --- (Depth: %d, Element: %d)\n", $name, $this->getDepth(), @$this->elements[$this->getDepth()]);
        $callback = array($this->decorator, $name);
        is_callable($callback) && call_user_func($callback);
    }
    public function beginElement()
    {
        $this->event('beginElement');
    }
    public function beginChildren()
    {
        $this->event('beginChildren');
    }
    public function endChildren()
    {
        $this->testEndElement();
        $this->event('endChildren');
    }
    private function testEndElement($depthOffset = 0)
    {
        $depth = $this->getDepth() + $depthOffset;      
        isset($this->elements[$depth]) || $this->elements[$depth] = 0;
        $this->elements[$depth] && $this->event('endElement');

    }
    public function nextElement()
    {
        $this->testEndElement();
        $this->event('{nextElement}');
        $this->event('beginElement');       
        $this->elements[$this->getDepth()] = 1;
    } 
    public function beginIteration()
    {
        $this->event('beginIteration');
    }
    public function endIteration()
    {
        $this->testEndElement();
        $this->event('endIteration');       
    }
}

class ListDecorator
{
    private $iterator;
    public function __construct(RecursiveListIterator $iterator)
    {
        $this->iterator = $iterator;
    }
    public function inset($add = 0)
    {
        return str_repeat('  ', $this->iterator->getDepth()*2+$add);
    }
    public function beginElement()
    {
        printf("%s<li>\n", $this->inset(1));
    }
    public function endElement()
    {
        printf("%s</li>\n", $this->inset(1));
    }
    public function beginChildren()
    {
        printf("%s<ul>\n", $this->inset());
    }
    public function endChildren()
    {
        printf("%s</ul>\n", $this->inset());
    }
    public function beginIteration()
    {
        printf("%s<ul>\n", $this->inset());
    }
    public function endIteration()
    {
        printf("%s</ul>\n", $this->inset());
    }
}


$root = new TreeNode($tree);
$it = new TreeNodesIterator(array($root));
$rit = new RecursiveListIterator($it);
$decor = new ListDecorator($rit);
$rit->addDecorator($decor);

foreach($rit as $item)
{
    $inset = $decor->inset(2);
    printf("%s%s\n", $inset, $item->getName());
}

Outpupt:

<ul>
  <li>
    D
    <ul>
      <li>
        G
        <ul>
          <li>
            H
          </li>
          <li>
            F
          </li>
        </ul>
      </li>
      <li>
        E
        <ul>
          </li>
          <li>
            A
          </li>
          <li>
            C
            <ul>
              <li>
                B
              </li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
  </li>
</ul>

演示(PHP 5.2变体)

一个可能的变体是迭代器,它迭代任何RecursiveIterator并提供对可能发生的所有事件的迭代。 foreach循环内的开关/案例可以处理事件。

有关:

  • 带有RecursiveArrayIterator的嵌套列表
  • RecursiveIteratorIterator类
hakre answered 2019-08-13T00:58:57Z
8 votes

好吧,首先我将键值对的直接数组转换为分层数组

function convertToHeiarchical(array $input) {
    $parents = array();
    $root = array();
    $children = array();
    foreach ($input as $item) {
        $parents[$item['id']] = &$item;
        if ($item['parent_id']) {
            if (!isset($children[$item['parent_id']])) {
                $children[$item['parent_id']] = array();
            }
            $children[$item['parent_id']][] = &$item;
        } else {
            $root = $item['id'];
        }
    }
    foreach ($parents as $id => &$item) {
        if (isset($children[$id])) {
            $item['children'] = $children[$id];
        } else {
            $item['children'] = array();
        }
    }
    return $parents[$root];
}

那可以将带有parent_id和id的平面数组转换为分层数组:

$item = array(
    'id' => 'A',
    'blah' => 'blah',
    'children' => array(
        array(
            'id' => 'B',
            'blah' => 'blah',
            'children' => array(
                array(
                    'id' => 'C',
                    'blah' => 'blah',
                    'children' => array(),
                ),
             ),
            'id' => 'D',
            'blah' => 'blah',
            'children' => array(
                array(
                    'id' => 'E',
                    'blah' => 'blah',
                    'children' => array(),
                ),
            ),
        ),
    ),
);

然后,只需创建一个渲染函数:

function renderItem($item) {
    $out = "Your OUtput For Each Item Here";
    $out .= "<ul>";
    foreach ($item['children'] as $child) {
        $out .= "<li>".renderItem($child)."</li>";
    }
    $out .= "</ul>";
    return $out;
}
ircmaxell answered 2019-08-13T00:59:38Z
5 votes

虽然亚历山大 - 康斯坦丁诺夫的解决方案起初可能看起来不那么容易,但就性能而言,它既是天才又是指数级的,这应该被认为是最好的答案。

谢谢你的配偶,我为你的荣誉做了一个基准,比较了这篇文章中提出的两个解决方案。

我有一个@ 250k平面树,有6个级别,我必须转换,我正在寻找一个更好的方法这样做,并避免递归迭代。

递归与参考:

// Generate a 6 level flat tree
$root = null;
$lvl1 = 13;
$lvl2 = 11;
$lvl3 = 7;
$lvl4 = 5;
$lvl5 = 3;
$lvl6 = 1;    
$flatTree = [];
for ($i = 1; $i <= 450000; $i++) {
    if ($i % 3 == 0)  { $lvl5 = $i; $flatTree[$lvl6] = $lvl5; continue; }
    if ($i % 5 == 0)  { $lvl4 = $i; $flatTree[$lvl5] = $lvl4; continue; }
    if ($i % 7 == 0)  { $lvl3 = $i; $flatTree[$lvl3] = $lvl2; continue; }
    if ($i % 11 == 0) { $lvl2 = $i; $flatTree[$lvl2] = $lvl1; continue; }
    if ($i % 13 == 0) { $lvl1 = $i; $flatTree[$lvl1] = $root; continue; }
    $lvl6 = $i;
}

echo 'Array count: ', count($flatTree), PHP_EOL;

// Reference function
function treeByReference($flatTree)
{
    $flat = [];
    $tree = [];

    foreach ($flatTree as $child => $parent) {
        if (!isset($flat[$child])) {
            $flat[$child] = [];
        }
        if (!empty($parent)) {
            $flat[$parent][$child] =& $flat[$child];
        } else {
            $tree[$child] =& $flat[$child];
        }
    }

    return $tree;
}

// Recursion function
function treeByRecursion($flatTree, $root = null)
{
    $return = [];
    foreach($flatTree as $child => $parent) {
        if ($parent == $root) {
            unset($flatTree[$child]);
            $return[$child] = treeByRecursion($flatTree, $child);
        }
    }
    return $return ?: [];
}

// Benchmark reference
$t1 = microtime(true);
$tree = treeByReference($flatTree);
echo 'Reference: ', (microtime(true) - $t1), PHP_EOL;

// Benchmark recursion
$t2 = microtime(true);
$tree = treeByRecursion($flatTree);
echo 'Recursion: ', (microtime(true) - $t2), PHP_EOL;

输出不言自明:

Array count: 255493
Reference: 0.3259289264679 (less than 0.4s)
Recursion: 6604.9865279198 (almost 2h)
ntt answered 2019-08-13T01:00:34Z
2 votes

那么,要解析为UL和LI,它将是这样的:

$array = array (
    'H' => 'G'
    'F' => 'G'
    'G' => 'D'
    'E' => 'D'
    'A' => 'E'
    'B' => 'C'
    'C' => 'E'
    'D' => 'NULL'
);


recurse_uls ($array, 'NULL');

function recurse_uls ($array, $parent)
{
    echo '<ul>';
    foreach ($array as $c => $p)  {
        if ($p != $parent) continue;
        echo '<li>'.$c.'</li>';
        recurse_uls ($array, $c);
    }
    echo '</ul>';
}

但我很乐意看到一个解决方案并不需要你经常迭代数组......

arnorhs answered 2019-08-13T01:01:09Z
2 votes

这是我想出的:

$arr = array(
            'H' => 'G',
            'F' => 'G',
            'G' => 'D',
            'E' => 'D',
            'A' => 'E',
            'B' => 'C',
            'C' => 'E',
            'D' => null );

    $nested = parentChild($arr);
    print_r($nested);

    function parentChild(&$arr, $parent = false) {
      if( !$parent) { //initial call
         $rootKey = array_search( null, $arr);
         return array($rootKey => parentChild($arr, $rootKey));
      }else { // recursing through
        $keys = array_keys($arr, $parent);
        $piece = array();
        if($keys) { // found children, so handle them
          if( !is_array($keys) ) { // only one child
            $piece = parentChild($arr, $keys);
           }else{ // multiple children
             foreach( $keys as $key ){
               $piece[$key] = parentChild($arr, $key);
             }
           }
        }else {
           return $parent; //return the main tag (no kids)
        }
        return $piece; // return the array built via recursion
      }
    }

输出:

Array
(
    [D] => Array
        (
            [G] => Array
                (
                    [H] => H
                    [F] => F
                )

            [E] => Array
                (
                    [A] => A
                    [C] => Array
                        (
                            [B] => B
                        )    
                )    
        )    
)
Dan Heberden answered 2019-08-13T01:01:32Z
0 votes

如何创建动态树视图和菜单

第1步:首先我们将在mysql数据库中创建treeview表。 此表包含四个column.id是任务ID,name是任务名称。

-
-- Table structure for table `treeview_items`
--

CREATE TABLE IF NOT EXISTS `treeview_items` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(200) NOT NULL,
  `title` varchar(200) NOT NULL,
  `parent_id` varchar(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ;

--
-- Dumping data for table `treeview_items`
--

INSERT INTO `treeview_items` (`id`, `name`, `title`, `parent_id`) VALUES
(1, 'task1', 'task1title', '2'),
(2, 'task2', 'task2title', '0'),
(3, 'task3', 'task1title3', '0'),
(4, 'task4', 'task2title4', '3'),
(5, 'task4', 'task1title4', '3'),
(6, 'task5', 'task2title5', '5');

第2步:树视图递归方法我创建了下面的树createTreeView()方法,如果当前任务id大于prev task id,则调用recursive。

function createTreeView($array, $currentParent, $currLevel = 0, $prevLevel = -1) {

foreach ($array as $categoryId => $category) {

if ($currentParent == $category['parent_id']) {                       
    if ($currLevel > $prevLevel) echo " <ol class='tree'> "; 

    if ($currLevel == $prevLevel) echo " </li> ";

    echo '<li> <label for="subfolder2">'.$category['name'].'</label> <input type="checkbox" name="subfolder2"/>';

    if ($currLevel > $prevLevel) { $prevLevel = $currLevel; }

    $currLevel++; 

    createTreeView ($array, $categoryId, $currLevel, $prevLevel);

    $currLevel--;               
    }   

}

if ($currLevel == $prevLevel) echo " </li>  </ol> ";

}

第3步:创建索引文件以显示树视图。这是treeview示例的主要文件,我们将使用所需参数调用createTreeView()方法。

 <body>
<link rel="stylesheet" type="text/css" href="_styles.css" media="screen">
<?php
mysql_connect('localhost', 'root');
mysql_select_db('test');


$qry="SELECT * FROM treeview_items";
$result=mysql_query($qry);


$arrayCategories = array();

while($row = mysql_fetch_assoc($result)){ 
 $arrayCategories[$row['id']] = array("parent_id" => $row['parent_id'], "name" =>                       
 $row['name']);   
  }
?>
<div id="content" class="general-style1">
<?php
if(mysql_num_rows($result)!=0)
{
?>
<?php 

createTreeView($arrayCategories, 0); ?>
<?php
}
?>

</div>
</body>

第4步:创建CSS文件style.css这里我们将编写所有css相关的类,目前我正在使用命令列表来创建树视图。 你也可以在这里改变图像路径。

img { border: none; }
input, select, textarea, th, td { font-size: 1em; }

/* CSS Tree menu styles */
ol.tree
{
    padding: 0 0 0 30px;
    width: 300px;
}
    li 
    { 
        position: relative; 
        margin-left: -15px;
        list-style: none;
    }
    li.file
    {
        margin-left: -1px !important;
    }
        li.file a
        {
            background: url(document.png) 0 0 no-repeat;
            color: #fff;
            padding-left: 21px;
            text-decoration: none;
            display: block;
        }
        li.file a[href *= '.pdf']   { background: url(document.png) 0 0 no-repeat; }
        li.file a[href *= '.html']  { background: url(document.png) 0 0 no-repeat; }
        li.file a[href $= '.css']   { background: url(document.png) 0 0 no-repeat; }
        li.file a[href $= '.js']        { background: url(document.png) 0 0 no-repeat; }
    li input
    {
        position: absolute;
        left: 0;
        margin-left: 0;
        opacity: 0;
        z-index: 2;
        cursor: pointer;
        height: 1em;
        width: 1em;
        top: 0;
    }
        li input + ol
        {
            background: url(toggle-small-expand.png) 40px 0 no-repeat;
            margin: -0.938em 0 0 -44px; /* 15px */
            height: 1em;
        }
        li input + ol > li { display: none; margin-left: -14px !important; padding-left: 1px; }
    li label
    {
        background: url(folder-horizontal.png) 15px 1px no-repeat;
        cursor: pointer;
        display: block;
        padding-left: 37px;
    }

    li input:checked + ol
    {
        background: url(toggle-small.png) 40px 5px no-repeat;
        margin: -1.25em 0 0 -44px; /* 20px */
        padding: 1.563em 0 0 80px;
        height: auto;
    }
        li input:checked + ol > li { display: block; margin: 0 0 0.125em;  /* 2px */}
        li input:checked + ol > li:last-child { margin: 0 0 0.063em; /* 1px */ }

更多细节

answered 2019-08-13T01:02:30Z
translate from https://stackoverflow.com:/questions/2915748/convert-a-series-of-parent-child-relationships-into-a-hierarchical-tree