How to make shortest code?

I use the following code to insert multi array to database:

foreach($request->category as $k => $v){
                $category[] = array(
                    "category_id" => $v,
                    "announcement_id" => $announcement->id
                );
            }

            AnnouncementCategory::insert($category);

So, input data is POST array $request->category. I need to refactoring this code

I tried this code:

$announcement->categories()->attach($request->category);

In model Announcement I have:

 public function categories()
    {
        return $this->hasMany("App\AnnouncementCategory", "announcement_id", "id");
    }

Solved

If you define in your Announcement model relationship like this:

public function categories() 
{
   return $this->belongsToMany(AnnouncementCategory::class);
}

you can do it like this:

$announcement->categories()->attach($request->category);

EDIT

I see you updated your question and added categories relationship. But looking at your code, AnnounceCategory is rather pivot table, so you should use belongsToMany as I showed instead of hasMany

You can do it in one line if the request matches the columns:

AnnouncementCategory::insert($request->all());

Then in your AnnouncementCategory model, make sure you declare the protected $fillable array where you specify which field could be populated.