On the parameterized complexity of the fixed alphabet shortest common supersequence and longest common subsequence problems

  • Authors:
  • Krzysztof Pietrzak

  • Affiliations:
  • Institute of Theoretical Computer Science, ETH Zentrum IFW E41, Haldeneggsteig 4, CH-8092 Zurich, Switzerland

  • Venue:
  • Journal of Computer and System Sciences - Special issue on Parameterized computation and complexity
  • Year:
  • 2003

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Abstract

We show that the fixed alphabet shortest common supersequence (SCS) and the fixed alphabet longest common subsequence (LCS) problems parameterized in the number of strings are W[1]-hard. Unless W[1] = FPT, this rules out the existence of algorithms with time complexity of O(f(k)nα) for those problems. Here n is the size of the problem instance, α is constant, k is the number of strings and f is any function of k. The fixed alphabet version of the LCS problem is of particular interest considering the importance of sequence comparison (e.g. multiple sequence alignment) in the fixed length alphabet world of DNA and protein sequences.