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！
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