public function delete(Request $request)
 {
     $this->validate($request, ['solution_id' => 'required|numeric']);
     $solution_id = $request->input('solution_id');
     $solution = Solution::where('id', $solution_id)->where('deleted', false)->where('user_id', Auth::user()->id)->first();
     if (!$solution) {
         abort(404);
     }
     $solution->deleted = true;
     $pass = $solution->save();
     $this->clearCache($solution);
     if ($pass) {
         Alert::setSuccessAlert(Lang::get('app.deleted_solution'));
     } else {
         Log::alert(__METHOD__ . '(' . __FILE__ . ')', array('solution_id' => $solution->id, 'user_id' => Auth::user()->id));
         Alert::setErrorAlert(Lang::get('app.unknown_error'));
     }
     Statistic::SubSolution();
     return redirect()->action('UserController@solutions');
 }