What would edmonds do? augmenting paths and witnesses for degree-bounded MSTs

  • Authors:
  • Kamalika Chaudhuri;Satish Rao;Samantha Riesenfeld;Kunal Talwar

  • Affiliations:
  • UC Berkeley;UC Berkeley;UC Berkeley;Microsoft Research, Redmond, WA

  • Venue:
  • APPROX'05/RANDOM'05 Proceedings of the 8th international workshop on Approximation, Randomization and Combinatorial Optimization Problems, and Proceedings of the 9th international conference on Randamization and Computation: algorithms and techniques
  • Year:
  • 2005

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Abstract

Given a graph and degree upper bounds on vertices, the BDMST problem requires us to find the minimum cost spanning tree respecting the given degree bounds.Könemann and Ravi [10,11] give bicriteria approximation algorithms for the problem using local search techniques of Fischer [5]. For a graph with a cost C, degree B spanning tree, and parameters b, w 1, their algorithm produces a tree whose cost is at most wC and whose degree is at most $\frac{w}{w-1}bB + \log_b n.$ We give a polynomial-time algorithm that finds a tree of optimal cost and with maximum degree at most bB + 2(b+1)logbn. We also give a quasi-polynomial algorithm which produces a tree of optimal cost C and maximum degree bounded by B + O(log n/loglog n). Our algorithms work when there are upper as well as lower bounds on the degrees of the vertices.