我們知道很多開源軟件的無限分類都是采用遞歸的算法，但是我們知道遞歸即浪費時間，又浪費空間（內存），
上次我也分享了個我自己原創的無限分類生成樹的方法，一熱心php高手網友給我提出了寶貴的建議，我測試了一下，這段代碼的時間非常之短參考： http://www.oschina.net/code/snippet_98719_11296，我再次整理了一下，發現數據庫查詢出數據之後，我們就已經定好了鍵值，因而實踐中，我們一般會在model中查詢出格式化成主鍵值對應數據的形式，因而我們可以直接用這樣的數據，就少了一層循環。代碼也非常簡潔。
原來的代碼：
function genTree($items,$id='id',$pid='pid',$son = 'children'){
$tree = array(); //格式化的樹
$tmpMap = array(); //臨時扁平數據
foreach ($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;
}
$items1 = array(
array('id' => 1, 'pid' => 0, 'name' => '一級11' ),
array('id' => 11, 'pid' => 0, 'name' => '一級12' ),
array('id' => 2, 'pid' => 1, 'name' => '二級21' ),
array('id' => 10, 'pid' => 11, 'name' => '二級22' ),
array('id' => 3, 'pid' => 1, 'name' => '二級23' ),
array('id' => 12, 'pid' => 11, 'name' => '二級24' ),
array('id' => 9, 'pid' => 1, 'name' => '二級25' ),
array('id' => 14, 'pid' => 1, 'name' => '二級26' ),
array('id' => 4, 'pid' => 9, 'name' => '三級31' ),
array('id' => 6, 'pid' => 9, 'name' => '三級32' ),
array('id' => 7, 'pid' => 4, 'name' => '四級41' ),
array('id' => 8, 'pid' => 4, 'name' => '四級42' ),
array('id' => 5, 'pid' => 4, 'name' => '四級43' ),
array('id' => 13, 'pid' => 4, 'name' => '四級44' ),
array('id' => 15, 'pid' => 8, 'name' => '五級51' ),
array('id' => 16, 'pid' => 8, 'name' => '五級52' ),
array('id' => 17, 'pid' => 8, 'name' => '五級53' ),
array('id' => 18, 'pid' => 16, 'name' => '六級64' ),
);
var_dump(genTree($items1));
以下是補充：
/**
* 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();
}
/**
* 將數據格式化成樹形結構
* @author Xuefen.Tong
* @param array $items
* @return array
*/
function genTree9($items) {
$tree = array(); //格式化好的樹
foreach ($items as $item)
if (isset($items[$item['pid']]))
$items[$item['pid']]['son'][] = &$items[$item['id']];
else
$tree[] = &$items[$item['id']];
return $tree;
}
$items = array(
1 => array('id' => 1, 'pid' => 0, 'name' => '江西省'),
2 => array('id' => 2, 'pid' => 0, 'name' => '黑龍江省'),
3 => array('id' => 3, 'pid' => 1, 'name' => '南昌市'),
4 => array('id' => 4, 'pid' => 2, 'name' => '哈爾濱市'),
5 => array('id' => 5, 'pid' => 2, 'name' => '雞西市'),
6 => array('id' => 6, 'pid' => 4, 'name' => '香坊區'),
7 => array('id' => 7, 'pid' => 4, 'name' => '南崗區'),
8 => array('id' => 8, 'pid' => 6, 'name' => '和興路'),
9 => array('id' => 9, 'pid' => 7, 'name' => '西大直街'),
10 => array('id' => 10, 'pid' => 8, 'name' => '東北林業大學'),
11 => array('id' => 11, 'pid' => 9, 'name' => '哈爾濱工業大學'),
12 => array('id' => 12, 'pid' => 8, 'name' => '哈爾濱師范大學'),
13 => array('id' => 13, 'pid' => 1, 'name' => '贛州市'),
14 => array('id' => 14, 'pid' => 13, 'name' => '贛縣'),
15 => array('id' => 15, 'pid' => 13, 'name' => '於都縣'),
16 => array('id' => 16, 'pid' => 14, 'name' => '茅店鎮'),
17 => array('id' => 17, 'pid' => 14, 'name' => '大田鄉'),
18 => array('id' => 18, 'pid' => 16, 'name' => '義源村'),
19 => array('id' => 19, 'pid' => 16, 'name' => '上壩村'),
);
print_r(genTree5($items));
print_r(genTree9($items));
//後者輸出格式，前者類似，只是數組鍵值不一樣，不過不影響數據結構
/*
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] => 贛州市
[son] => Array
(
[0] => Array
(
[id] => 14
[pid] => 13
[name] => 贛縣
[son] => Array
(
[0] => Array
(
[id] => 16
[pid] => 14
[name] => 茅店鎮
[son] => Array
(
[0] => Array
(
[id] => 18
[pid] => 16
[name] => 義源村
)
[1] => Array
(
[id] => 19
[pid] => 16
[name] => 上壩村
)
)
)
[1] => Array
(
[id] => 17
[pid] => 14
[name] => 大田鄉
)
)
)
[1] => Array
(
[id] => 15
[pid] => 13
[name] => 於都縣
)
)
)
)
)
[1] => Array
(
[id] => 2
[pid] => 0
[name] => 黑龍江省
[son] => Array
(
[0] => Array
(
[id] => 4
[pid] => 2
[name] => 哈爾濱市
[son] => Array
(
[0] => Array
(
[id] => 6
[pid] => 4
[name] => 香坊區
[son] => Array
(
[0] => Array
(
[id] => 8
[pid] => 6
[name] => 和興路
[son] => Array
(
[0] => Array
(
[id] => 10
[pid] => 8
[name] =>
東北林業大學
)
[1] => Array
(
[id] => 12
[pid] => 8
[name] =>
哈爾濱師范大學
)
)
)
)
)
[1] => Array
(
[id] => 7
[pid] => 4
[name] => 南崗區
[son] => Array
(
[0] => Array
(
[id] => 9
[pid] => 7
[name] => 西大直街
[son] => Array
(
[0] => Array
(
[id] => 11
[pid] => 9
[name] =>
哈爾濱工業大學
)
)
)
)
)
)
)
[1] => Array
(
[id] => 5
[pid] => 2
[name] => 雞西市
)
)
)
)*/
極其簡單有效！！！非常受用！
