無限級分類是開發中常見的情況了,在這里我收藏了下并整理了下常見的無限極分類算法總結歸納.

<?php $arr = [1=>['id'=>1,'name'=>'家居','father'=>NULL],2=>['id'=>2,'name'=>'服裝','father'=>NULL],3=>['id'=>3,'name'=>'護膚品','father'=>NULL],4=>['id'=>4,'name'=>'生活日用','father'=>1],5=>['id'=>5,'name'=>'家庭裝修','father'=>1],6=>['id'=>6,'name'=>'廚房衛浴','father'=>1],7=>['id'=>7,'name'=>'男裝','father'=>2],8=>['id'=>8,'name'=>'女裝','father'=>2],9=>['id'=>9,'name'=>'面部護膚','father'=>3],10=>['id'=>10,'name'=>'補水保濕','father'=>9],11=>['id'=>11,'name'=>'收納用品','father'=>4],12=>['id'=>12,'name'=>'牛仔褲','father'=>7], ]; function generateTree($items){$tree = array();foreach($items as $item){if(isset($items[$item['father']])){$items[$item['father']]['son'][] = &$items[$item['id']];}else{$tree[] = &$items[$item['id']];}}return $tree; } $tree = generateTree($arr); print_r($tree); ?>

輸出：

Array ([0] => Array([id] => 1[name] => 家居[father] => [son] => Array([0] => Array([id] => 4[name] => 生活日用[father] => 1[son] => Array([0] => Array([id] => 11[name] => 收納用品[father] => 4)))[1] => Array([id] => 5[name] => 家庭裝修[father] => 1)[2] => Array([id] => 6[name] => 廚房衛浴[father] => 1)))[1] => Array([id] => 2[name] => 服裝[father] => [son] => Array([0] => Array([id] => 7[name] => 男裝[father] => 2[son] => Array([0] => Array([id] => 12[name] => 牛仔褲[father] => 7)))[1] => Array([id] => 8[name] => 女裝[father] => 2)))[2] => Array([id] => 3[name] => 護膚品[father] => [son] => Array([0] => Array([id] => 9[name] => 面部護膚[father] => 3[son] => Array([0] => Array([id] => 10[name] => 補水保濕[father] => 9))))))

分析:

這個算法利用了循環迭代,將線性結構按照父子關系以樹形結構輸出,算法的關鍵在于使用了引用.

優點:速度快,效率高.

缺點:數組的key值必須與id值相同,不便于取出數據(使用遞歸獲取數據)

我們再看下遞歸的實現：

<?php $arr = [1=>['id'=>1,'name'=>'家居','father'=>NULL],2=>['id'=>2,'name'=>'服裝','father'=>NULL],3=>['id'=>3,'name'=>'護膚品','father'=>NULL],4=>['id'=>4,'name'=>'生活日用','father'=>1],5=>['id'=>5,'name'=>'家庭裝修','father'=>1],6=>['id'=>6,'name'=>'廚房衛浴','father'=>1],7=>['id'=>7,'name'=>'男裝','father'=>2],8=>['id'=>8,'name'=>'女裝','father'=>2],9=>['id'=>9,'name'=>'面部護膚','father'=>3],10=>['id'=>10,'name'=>'補水保濕','father'=>9],11=>['id'=>11,'name'=>'收納用品','father'=>4],12=>['id'=>12,'name'=>'牛仔褲','father'=>7], ]; function generateTree($arr,$id,$step){static $tree=[];foreach($arr as $key=>$val) {if($val['father'] == $id) {$flag = str_repeat('└―',$step);$val['name'] = $flag.$val['name'];$tree[] = $val;generateTree($arr , $val['id'] ,$step+1);}}return $tree; } $tree = generateTree($arr,0,0); foreach ($tree as $val){echo $val['name'].'<br>'; } ?>

輸出：

家居 └―生活日用 └―└―收納用品 └―家庭裝修 └―廚房衛浴 服裝 └―男裝 └―└―牛仔褲 └―女裝 護膚品 └―面部護膚 └―└―補水保濕

分析:

利用了遞歸,數組的key值與id值可以不相同,最后以順序的結構輸出數組

優點:方便遍歷,查找父子元素

缺點:php不擅長遞歸,數據量大的情況下效率會顯著降低
總結：兩種方法各有利弊，后者不適合大數據下使用，前者推薦吧

總結

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