Sorting by transpositions is difficult

  • Authors:
  • Laurent Bulteau;Guillaume Fertin;Irena Rusu

  • Affiliations:
  • Laboratoire d'Informatique de Nantes-Atlantique, UMR, CNRS, Université de Nantes, Nantes Cedex 3, France;Laboratoire d'Informatique de Nantes-Atlantique, UMR, CNRS, Université de Nantes, Nantes Cedex 3, France;Laboratoire d'Informatique de Nantes-Atlantique, UMR, CNRS, Université de Nantes, Nantes Cedex 3, France

  • Venue:
  • ICALP'11 Proceedings of the 38th international colloquim conference on Automata, languages and programming - Volume Part I
  • Year:
  • 2011

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Abstract

In comparative genomics, a transposition is an operation that exchanges two consecutive sequences of genes in a genome. The transposition distance, that is, the minimum number of transpositions needed to transform a genome into another, can be considered as a relevant evolutionary distance. The problem of computing this distance when genomes are represented by permutations, called the SORTING BY TRANSPOSITIONS problem (SBT), has been introduced by Bafna and Pevzner [3] in 1995. It has naturally been the focus of a number of studies, but the computational complexity of this problem has remained undetermined for 15 years. In this paper, we answer this long-standing open question by proving that the SORTING BY TRANSPOSITIONS problem is NP-hard. As a corollary of our result, we also prove that the following problem from [10] is NP-hard: given a permutation π, is it possible to sort π using db(π)/3 permutations, where db(π) is the number of breakpoints of π?