Limited Nondeterminism of Input-Driven Pushdown Automata: Decidability and Complexity

  • Yo-Sub Han
  • Sang-Ki Ko
  • Kai SalomaaEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11612)


We study the decidability and computational complexity for several decision problems related to limited nondeterminism of finite-state automata equipped with a pushdown stack. Ambiguity and tree width are two measures of nondeterminism considered in the literature. As a main result, we prove that the problem of deciding whether or not the tree width of a nondeterministic pushdown automaton is finite is decidable in polynomial time. We also prove that the k-tree width problem for nondeterministic input-driven pushdown automata (respectively, nondeterministic finite automata) is complete for exponential time (respectively, for polynomial space).


Nondeterminism Tree width Ambiguity Input-driven pushdown automata 


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Authors and Affiliations

  1. 1.Department of Computer ScienceYonsei UniversitySeoulRepublic of Korea
  2. 2.AI Research CenterKorea Electronics Technology InstituteSeongnamRepublic of Korea
  3. 3.School of ComputingQueen’s UniversityKingstonCanada

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