[PHP知识库]递归算法 ---PHP

1，通过递归实现阶乘

function multi($n){

    if($n == 0){
        return 1 ;//终止递归
    }
    $value = $n * multi($n-1);
    return $value;
}

2，通过递归，实现斐波那契数列

function Fib($n){
    if($n ==1||$n==0){
        return 1;//终止递归
    }
    $value = Fib($n-1)+Fib($n-2);
    return $value;
}
echo Fib(6);

$category = [
       [
           'id' =>1,
           'name'=>'男装',
           'pid'=>0,
       ],
       [
           'id'=>2,
            'name'=>'女装',
            'pid'=>0,

       ],
       [
           'id'=>3,
           'name'=>'男士外套',
           'pid' =>1,
           ],
         [
             'id' =>4,
             'name'=>'夹克',
             'pid' =>3,

         ],
         [
             'id'=>5,
             'name'=>'棉衣',
             'pid'=> 3,
         ],
];

3，通过父类ID获取所有的子类

function recursiveCategory($pid,$category){
    $data = [];
    foreach ($category as $item){
        if($item['pid']==$pid){
            $arr['id'] = $item['id'];
            $arr['name'] = $item['name'];
            $cate = recursiveCategory($item['id'],$category);
            if(!empty($cate)){
                $arr[] =$cate;
            }
            $data[] = $arr;
            unset($arr);
        }
    }
    return $data;
};

?

4， 通过子类获取所有父类

function getCategoryByChild($childId,$category){
    $data = [];
    foreach ($category as $item){
        if($item['id'] == $childId){
            $arr['id'] =$item['id'];
            $arr['name']= $item['name'];
            if($item['pid']!=0){
                $arr[] = getCategoryByChild($item['pid'],$category);
            }
            $data[]=$arr;
        }
    }
    return $data;
}