1. School of Computer Science, Shaanxi Normal University, Xi’an 710062, China
2. College of Computer, Qinghai Normal University, Xining 810008, China
3. Department of Mathematics, Qinghai Normal University, Xining 810008, China
4. Department of Mathematics, Southeast University, Nanjing 210096, China
5. Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia