PHP迭代與遞迴實現無限級分類

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無限級分類是開發中常見的情況,因此本文對常見的無限極分類演算法進行總結歸納.

1.迴圈迭代實現

 1 $arr = [ 2     1=>[‘id‘=>1,‘name‘=>‘父1‘,‘father‘=>NULL], 3     2=>[‘id‘=>2,‘name‘=>‘父2‘,‘father‘=>NULL], 4     3=>[‘id‘=>3,‘name‘=>‘父3‘,‘father‘=>NULL], 5     4=>[‘id‘=>4,‘name‘=>‘兒1-1‘,‘father‘=>1], 6     5=>[‘id‘=>5,‘name‘=>‘兒1-2‘,‘father‘=>1], 7     6=>[‘id‘=>6,‘name‘=>‘兒1-3‘,‘father‘=>1], 8     7=>[‘id‘=>7,‘name‘=>‘兒2-1‘,‘father‘=>2], 9     8=>[‘id‘=>8,‘name‘=>‘兒2-1‘,‘father‘=>2],10     9=>[‘id‘=>9,‘name‘=>‘兒3-1‘,‘father‘=>3],11     10=>[‘id‘=>10,‘name‘=>‘兒3-1-1‘,‘father‘=>9],12     11=>[‘id‘=>11,‘name‘=>‘兒1-1-1‘,‘father‘=>4],13     12=>[‘id‘=>12,‘name‘=>‘兒2-1-1‘,‘father‘=>7],14 ];15 function generateTree($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));

輸出:

分析:

這個演算法利用了迴圈迭代,將線性結構按照父子關係以樹形結構輸出,演算法的關鍵在於使用了引用.

優點:速度快,效率高.

缺點:數組的key值必須與id值相同,不便於取出資料(使用遞迴擷取資料)

2.遞迴實現

$arr = [    0=>[‘id‘=>1,‘name‘=>‘父1‘,‘father‘=>0],    1=>[‘id‘=>2,‘name‘=>‘父2‘,‘father‘=>0],    2=>[‘id‘=>3,‘name‘=>‘父3‘,‘father‘=>0],    3=>[‘id‘=>4,‘name‘=>‘兒1-1‘,‘father‘=>1],    4=>[‘id‘=>5,‘name‘=>‘兒1-2‘,‘father‘=>1],    5=>[‘id‘=>6,‘name‘=>‘兒1-3‘,‘father‘=>1],    6=>[‘id‘=>7,‘name‘=>‘兒2-1‘,‘father‘=>2],    7=>[‘id‘=>8,‘name‘=>‘兒2-1‘,‘father‘=>2],    8=>[‘id‘=>9,‘name‘=>‘兒3-1‘,‘father‘=>3],    9=>[‘id‘=>10,‘name‘=>‘兒3-1-1‘,‘father‘=>9],    10=>[‘id‘=>11,‘name‘=>‘兒1-1-1‘,‘father‘=>4],    11=>[‘id‘=>12,‘name‘=>‘兒2-1-1‘,‘father‘=>7],];function generateTree($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>‘;}

 

 輸出:

分析:

利用了遞迴,數組的key值與id值可以不相同,最後以順序的結構輸出數組

優點:方便遍曆,尋找父子項目

缺點:php不擅長遞迴,資料量大的情況下效率會顯著降低

PHP迭代與遞迴實現無限級分類