1. School of Computer Science and Engineering, Chongqing Three Gorges University, Chongqing 404100, China
2. Key Laboratory of Intelligent Information Processing and Control, Chongqing Three Gorges University, Wanzhou, Chongqing 404100, China
3. College of Computer Science, Chongqing University, Chongqing 400044, China
4. Department of Mathematics, University of Ibadan, Ibadan 200005, Nigeria