Randomised Enumeration of Small Witnesses Using a Decision Oracle

Author Kitty Meeks

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Kitty Meeks

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Kitty Meeks. Randomised Enumeration of Small Witnesses Using a Decision Oracle. In 11th International Symposium on Parameterized and Exact Computation (IPEC 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 63, pp. 22:1-22:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)


Many combinatorial problems involve determining whether a universe of n elements contains a witness consisting of k elements which have some specified property. In this paper we investigate the relationship between the decision and enumeration versions of such problems: efficient methods are known for transforming a decision algorithm into a search procedure that finds a single witness, but even finding a second witness is not so straightforward in general. In this paper we show that, if the decision version of the problem belongs to FPT, there is a randomised algorithm which enumerates all witnesses in time f(k)*poly(n)*N, where N is the total number of witnesses and f is a computable function. This also gives rise to an efficient algorithm to count the total number of witnesses when this number is small.
  • enumeration algorithms
  • parameterized complexity
  • randomized algorithms
  • color coding


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