Counting Paths in VPA Is Complete for #NC1

  • Andreas Krebs
  • Nutan Limaye
  • Meena Mahajan
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 6196)


We give a #NC 1 upper bound for the problem of counting accepting paths in any fixed visibly pushdown automaton. Our algorithm involves a non-trivial adaptation of the arithmetic formula evaluation algorithm of Buss, Cook, Gupta, Ramachandran ([9]). We also show that the problem is #NC 1 hard. Our results show that the difference between #BWBP and #NC 1 is captured exactly by the addition of a visible stack to a nondeterministic finite-state automata.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2010

Authors and Affiliations

  • Andreas Krebs
    • 1
  • Nutan Limaye
    • 2
  • Meena Mahajan
    • 3
  1. 1.University of TübingenGermany
  2. 2.Tata Institute of Fundamental ResearchMumbaiIndia
  3. 3.The Institute of Mathematical SciencesChennaiIndia

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