Complexity theory is the theory of determining the necessary resources for the solution of algorithmic problems and, therefore, the limits what is possible with the available resources. The results prevent the search for non-existing efficient algorithms. The theory of NP-completeness has influenced the development of all areas of computer science. New branches of complexity theory react to all new algorithmic concepts. This textbook considers randomization as a key concept. The chosen subjects have implications to concrete applications. The significance of complexity theory for today’s computer science is stressed.

The author is a full professor at the Computer Science Department of Dortmund University. He is the author of 8 monographs and more than 150 journal and conference articles. He was head of the German youth competition in computer science and has obtained the university medal for excellent teaching. He is an elected member of the German Academy of Sciences and was head of the committee reviewing computer research projects in Germany.