我们知道很多开源软件的无限分类都是采用递归的算法，但是我们知道递归即浪费时间，又浪费空间（内存），
上次我也分享了个我自己原创的无限分类生成树的方法，一热心php高手网友给我提出了宝贵的建议，我测试了一下，这段代码的时间非常之短参考： http://www.oschina.net/code/snippet_98719_11296，我再次整理了一下，发现数据库查询出数据之后，我们就已经定好了键值，因而实践中，我们一般会在model中查询出格式化成主键值对应数据的形式，因而我们可以直接用这样的数据，就少了一层循环。代码也非常简洁。
原来的代码：
function genTree($items,$id="id",$pid="pid",$son = "children"){
$tree = array(); //格式化的树
$tmpMap = array(); //临时扁平数据
foreach ($items as $item) {
$tmpMap[$item[$id]] = $item;
}
foreach ($items as $item) {
if (isset($tmpMap[$item[$pid]])) {
$tmpMap[$item[$pid]][$son][] = &$tmpMap[$item[$id]];
} else {
$tree[] = &$tmpMap[$item[$id]];
}
}
unset($tmpMap);
return $tree;
}
$items1 = array(
array("id" => 1, "pid" => 0, "name" => "一级11" ),
array("id" => 11, "pid" => 0, "name" => "一级12" ),
array("id" => 2, "pid" => 1, "name" => "二级21" ),
array("id" => 10, "pid" => 11, "name" => "二级22" ),
array("id" => 3, "pid" => 1, "name" => "二级23" ),
array("id" => 12, "pid" => 11, "name" => "二级24" ),
array("id" => 9, "pid" => 1, "name" => "二级25" ),
array("id" => 14, "pid" => 1, "name" => "二级26" ),
array("id" => 4, "pid" => 9, "name" => "三级31" ),
array("id" => 6, "pid" => 9, "name" => "三级32" ),
array("id" => 7, "pid" => 4, "name" => "四级41" ),
array("id" => 8, "pid" => 4, "name" => "四级42" ),
array("id" => 5, "pid" => 4, "name" => "四级43" ),
array("id" => 13, "pid" => 4, "name" => "四级44" ),
array("id" => 15, "pid" => 8, "name" => "五级51" ),
array("id" => 16, "pid" => 8, "name" => "五级52" ),
array("id" => 17, "pid" => 8, "name" => "五级53" ),
array("id" => 18, "pid" => 16, "name" => "六级64" ),
);
var_dump(genTree($items1));
以下是补充：
/**
* 此方法由@Tonton 提供
* http://my.oschina.net/u/918697
* @date 2012-12-12
*/
function genTree5($items) {
foreach ($items as $item)
$items[$item["pid"]]["son"][$item["id"]] = &$items[$item["id"]];
return isset($items[0]["son"]) ? $items[0]["son"] : array();
}
/**
* 将数据格式化成树形结构
* @author Xuefen.Tong
* @param array $items
* @return array
*/
function genTree9($items) {
$tree = array(); //格式化好的树
foreach ($items as $item)
if (isset($items[$item["pid"]]))
$items[$item["pid"]]["son"][] = &$items[$item["id"]];
else
$tree[] = &$items[$item["id"]];
return $tree;
}
$items = array(
1 => array("id" => 1, "pid" => 0, "name" => "江西省"),
2 => array("id" => 2, "pid" => 0, "name" => "黑龙江省"),
3 => array("id" => 3, "pid" => 1, "name" => "南昌市"),
4 => array("id" => 4, "pid" => 2, "name" => "哈尔滨市"),
5 => array("id" => 5, "pid" => 2, "name" => "鸡西市"),
6 => array("id" => 6, "pid" => 4, "name" => "香坊区"),
7 => array("id" => 7, "pid" => 4, "name" => "南岗区"),
8 => array("id" => 8, "pid" => 6, "name" => "和兴路"),
9 => array("id" => 9, "pid" => 7, "name" => "西大直街"),
10 => array("id" => 10, "pid" => 8, "name" => "东北林业大学"),
11 => array("id" => 11, "pid" => 9, "name" => "哈尔滨工业大学"),
12 => array("id" => 12, "pid" => 8, "name" => "哈尔滨师范大学"),
13 => array("id" => 13, "pid" => 1, "name" => "赣州市"),
14 => array("id" => 14, "pid" => 13, "name" => "赣县"),
15 => array("id" => 15, "pid" => 13, "name" => "于都县"),
16 => array("id" => 16, "pid" => 14, "name" => "茅店镇"),
17 => array("id" => 17, "pid" => 14, "name" => "大田乡"),
18 => array("id" => 18, "pid" => 16, "name" => "义源村"),
19 => array("id" => 19, "pid" => 16, "name" => "上坝村"),
);
print_r(genTree5($items));
print_r(genTree9($items));
//后者输出格式，前者类似，只是数组键值不一样，不过不影响数据结构
/*
Array
(
[0] => Array
(
[id] => 1
[pid] => 0
[name] => 江西省
[son] => Array
(
[0] => Array
(
[id] => 3
[pid] => 1
[name] => 南昌市
)
[1] => Array
(
[id] => 13
[pid] => 1
[name] => 赣州市
[son] => Array
(
[0] => Array
(
[id] => 14
[pid] => 13
[name] => 赣县
[son] => Array
(
[0] => Array
(
[id] => 16
[pid] => 14
[name] => 茅店镇
[son] => Array
(
[0] => Array
(
[id] => 18
[pid] => 16
[name] => 义源村
)
[1] => Array
(
[id] => 19
[pid] => 16
[name] => 上坝村
)
)
)
[1] => Array
(
[id] => 17
[pid] => 14
[name] => 大田乡
)
)
)
[1] => Array
(
[id] => 15
[pid] => 13
[name] => 于都县
)
)
)
)
)
[1] => Array
(
[id] => 2
[pid] => 0
[name] => 黑龙江省
[son] => Array
(
[0] => Array
(
[id] => 4
[pid] => 2
[name] => 哈尔滨市
[son] => Array
(
[0] => Array
(
[id] => 6
[pid] => 4
[name] => 香坊区
[son] => Array
(
[0] => Array
(
[id] => 8
[pid] => 6
[name] => 和兴路
[son] => Array
(
[0] => Array
(
[id] => 10
[pid] => 8
[name] =>
东北林业大学
)
[1] => Array
(
[id] => 12
[pid] => 8
[name] =>
哈尔滨师范大学
)
)
)
)
)
[1] => Array
(
[id] => 7
[pid] => 4
[name] => 南岗区
[son] => Array
(
[0] => Array
(
[id] => 9
[pid] => 7
[name] => 西大直街
[son] => Array
(
[0] => Array
(
[id] => 11
[pid] => 9
[name] =>
哈尔滨工业大学
)
)
)
)
)
)
)
[1] => Array
(
[id] => 5
[pid] => 2
[name] => 鸡西市
)
)
)
)*/
极其简单有效！！！非常受用！
