无限级分类是开发中常见的情况,因此本文对常见的无限极分类算法进行总结归纳.
1.循环迭代实现
1 $arr = [ 2 ????1=>[‘id‘=>1,‘name‘=>‘父1‘,‘father‘=>NULL], 3 ????2=>[‘id‘=>2,‘name‘=>‘父2‘,‘father‘=>NULL], 4 ????3=>[‘id‘=>3,‘name‘=>‘父3‘,‘father‘=>NULL], 5 ????4=>[‘id‘=>4,‘name‘=>‘儿1-1‘,‘father‘=>1], 6 ????5=>[‘id‘=>5,‘name‘=>‘儿1-2‘,‘father‘=>1], 7 ????6=>[‘id‘=>6,‘name‘=>‘儿1-3‘,‘father‘=>1], 8 ????7=>[‘id‘=>7,‘name‘=>‘儿2-1‘,‘father‘=>2], 9 ????8=>[‘id‘=>8,‘name‘=>‘儿2-1‘,‘father‘=>2],10 ????9=>[‘id‘=>9,‘name‘=>‘儿3-1‘,‘father‘=>3],11 ????10=>[‘id‘=>10,‘name‘=>‘儿3-1-1‘,‘father‘=>9],12 ????11=>[‘id‘=>11,‘name‘=>‘儿1-1-1‘,‘father‘=>4],13 ????12=>[‘id‘=>12,‘name‘=>‘儿2-1-1‘,‘father‘=>7],14 ];15 function generateTree($items){16 ????$tree = array();17 ????foreach($items as $item){18 ????????if(isset($items[$item[‘father‘]])){19 ????????????$items[$item[‘father‘]][‘son‘][] = &$items[$item[‘id‘]]; 20 ????????}else{21 ????????????$tree[] = &$items[$item[‘id‘]];22 ????????}23 ????}24 ????return $tree;25 }26 $tree = generateTree($arr);27 print_r(json_encode($tree));输出:
分析:
这个算法利用了循环迭代,将线性结构按照父子关系以树形结构输出,算法的关键在于使用了引用.
优点:速度快,效率高.
缺点:数组的key值必须与id值相同,不便于取出数据(使用递归获取数据)
2.递归实现
$arr = [ ???0=>[‘id‘=>1,‘name‘=>‘父1‘,‘father‘=>0], ???1=>[‘id‘=>2,‘name‘=>‘父2‘,‘father‘=>0], ???2=>[‘id‘=>3,‘name‘=>‘父3‘,‘father‘=>0], ???3=>[‘id‘=>4,‘name‘=>‘儿1-1‘,‘father‘=>1], ???4=>[‘id‘=>5,‘name‘=>‘儿1-2‘,‘father‘=>1], ???5=>[‘id‘=>6,‘name‘=>‘儿1-3‘,‘father‘=>1], ???6=>[‘id‘=>7,‘name‘=>‘儿2-1‘,‘father‘=>2], ???7=>[‘id‘=>8,‘name‘=>‘儿2-1‘,‘father‘=>2], ???8=>[‘id‘=>9,‘name‘=>‘儿3-1‘,‘father‘=>3], ???9=>[‘id‘=>10,‘name‘=>‘儿3-1-1‘,‘father‘=>9], ???10=>[‘id‘=>11,‘name‘=>‘儿1-1-1‘,‘father‘=>4], ???11=>[‘id‘=>12,‘name‘=>‘儿2-1-1‘,‘father‘=>7],];function generateTree($arr,$id,$step){ ???static $tree=[]; ???foreach($arr as $key=>$val) { ???????if($val[‘father‘] == $id) { ???????????$flg = str_repeat(‘└―‘,$step); ???????????$val[‘name‘] = $flg.$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>‘;}输出:
分析:
利用了递归,数组的key值与id值可以不相同,最后以顺序的结构输出数组
优点:方便遍历,查找父子元素
缺点:php不擅长递归,数据量大的情况下效率会显著降低
PHP迭代与递归实现无限级分类
原文地址：http://www.cnblogs.com/shenzikun1314/p/7467148.html