1. Institute of Computing Science and Technology, Guangzhou University, Guangzhou 510006, China
2. School of Computer Science of Information Technology, Qiannan Normal University for Nationalities, Duyun 558000, China
3. Department of Mathematics, Prince Sattam Bin Abdulaziz University, Al-Kharj 11991, Saudi Arabia
4. Department of Mathematics, University of the Punjab, Lahore 54590, Pakistan