This book constitutes the revised selected papers of the 20th International Workshop on
Combinatorial Algorithms held in June July 2009 in the castle of Hradec nad Moravicí Czech
Republic. The 41 papers included in this volume together with 5 invited papers were carefully
reviewed and selected from over 100 submissions. The topics dealt with are algorithms and data
structures applications combinatorial enumeration combinatorial optimization complexity
theory computational biology databases decompositions and combinatorial designs discrete
and computational geometry including graph drawing and graph theory and combinatorics.
