This volume contains papers selected for presentation at the 26th International Symposium on
Mathematical Foundations of Computer Science MFCS 2001 held in Mari ansk eL azn?e Czech
Republic August 27 31 2001. MFCS 2001 was organized by the Mathematical Institute (Academy of
S- ences of the Czech Republic) the Institute for Theoretical Computer Science (Charles
University Faculty of Mathematics and Physics) the Institute of C- puter Science (Academy of
Sciences of the Czech Republic) and Action M Agency. It was supported by the European Research
Consortium for Informatics and Mathematics the Czech Research Consortium for Informatics and
Ma- ematics and the European Association for Theoretical Computer Science. We gratefully
acknowledge the support of all these institutions. The series of MFCS symposia organized on a
rotating basis in Poland S- vakia and the Czech Republic has a well-established tradition.
The aim is to encourage high-quality research in all branches of theoretical computer science
and bring together specialists who do not usually meet at specialized confer- ? ences. Previous
meetings tookplace in Jablonna 1972 Strbsk e Pleso 1973 J- wisin 1974 Marian sk eL azn?e
1975 Gdan sk 1976 Tatransk a Lomnica 1977 Za- ? kopane 1978 Olomouc 1979 Rydzina 1980
Strbsk e Pleso 1981 Prague 1984 Bratislava 1986 Karlovy Vary 1988 Porabk a-Kozubnik
1989 Bansk aBystrica 1990 Kazimierz Dolny 1991 Prague 1992 Gdan sk 1993 Ko?sice 1994
Prague 1995 Krak ow 1996 Bratislava 1997 Brno 1998 Szklarska Por eba 1999 and
Bratislava 2000.
