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后，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;} $items = array( 1 => array('id' => 1, 'pid' => 0, 'name' => '江西省'), 2 => array('id' => 2, 'pid' => 0, 'name' => '黑龍江省'), 3 => array('id' => 3, 'pid' => 1, 'name' => '南昌市'), 4 => array('id' => 4, 'pid' => 2, 'name' => '哈爾濱市'), 5 => array('id' => 5, 'pid' => 2, 'name' => '雞西市'), 6 => array('id' => 6, 'pid' => 4, 'name' => '香坊區'), 7 => array('id' => 7, 'pid' => 4, 'name' => '南崗區'), 8 => array('id' => 8, 'pid' => 6, 'name' => '和興路'), 9 => array('id' => 9, 'pid' => 7, 'name' => '西大直街'), 10 => array('id' => 10, 'pid' => 8, 'name' => '東北林業大學'), 11 => array('id' => 11, 'pid' => 9, 'name' => '哈爾濱工業大學'), 12 => array('id' => 12, 'pid' => 8, 'name' => '哈爾濱師范大學'), 13 => array('id' => 13, 'pid' => 1, 'name' => '贛州市'), 14 => array('id' => 14, 'pid' => 13, 'name' => '贛縣'), 15 => array('id' => 15, 'pid' => 13, 'name' => '于都縣'), 16 => array('id' => 16, 'pid' => 14, 'name' => '茅店鎮'), 17 => array('id' => 17, 'pid' => 14, 'name' => '大田鄉'), 18 => array('id' => 18, 'pid' => 16, 'name' => '義源村'), 19 => array('id' => 19, 'pid' => 16, 'name' => '上壩村'),);print_r(genTree5($items));print_r(genTree9($items));//后者輸出格式，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] => 于都縣 ) ) ) ) ) [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！
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