Enumerating neighbour and closest strings

  • Authors:
  • Naomi Nishimura;Narges Simjour

  • Affiliations:
  • Cheriton School of Computer Science, University of Waterloo, Waterloo, Ontario, Canada;Cheriton School of Computer Science, University of Waterloo, Waterloo, Ontario, Canada

  • Venue:
  • IPEC'12 Proceedings of the 7th international conference on Parameterized and Exact Computation
  • Year:
  • 2012

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Abstract

We present the first parameterized enumeration algorithm for the neighbour string problem, where a neighbour string of n input strings, each of length ℓ, is a string that differs from input si in no more than di positions. The problem is NP-complete even when the di's are equal; this is the well-known closest string problem. Our new approach gives us the ability to tune the running time to optimize the algorithm for varying relative values of n and d= max idi. For strings over an alphabet Σ, we can choose a tuning constant λ to obtain an algorithm that runs in time O(nℓ+(nd)f(λ)(|Σ|−1)d 5(1+λ)d), where f is a function that decreases with increasing λ. When Σ={0,1}, the dependency on d is an asymptotic improvement over the previous best parameterized time bound of O(nℓ+nd3 6.7308d) for finding a single solution.