/*
     * 隨機處理邏輯
     * */
    private function _Rand($type, $num){
        if (intval($num) <= 0){ return false;}
        $problemArr = ProblemModel::getBaseArr(['state' => 1, 'type' => $type], ['id'], [], ['order' => SORT_DESC]);
        $problemArr = array_column($problemArr, 'id');

        
 
$PaperArr = PaperProblemModel::getBaseArr(['type' => $type], ['problem_id']);
        $PaperArr = array_column($PaperArr, 'problem_id');

        $d_count = count($problemArr);
        if ($d_count < $num) { $this->_error('資料表選題數量不夠', []);}

        $Arr = array_diff($problemArr, $PaperArr);
        
 
$count = count($Arr);
        if ($count < $num){
            $return = array_rand($problemArr, $num);
        } else {
            $problemArr = array_unique($Arr);
            $return = array_rand($problemArr, $num);
        }
        $res = [];
        foreach ($return  as $k => $v){
            
 
$res[$k] = $problemArr[$return[$k]];
        }
        return $res;
    }