Rectangular layouts and contact graphs

  • Authors:
  • Adam L. Buchsbaum;Emden R. Gansner;Cecilia M. Procopiuc;Suresh Venkatasubramanian

  • Affiliations:
  • AT&T Labs, Florham Park, NJ;AT&T Labs, Florham Park, NJ;AT&T Labs, Florham Park, NJ;University of Utah, Salt Lake City, UT

  • Venue:
  • ACM Transactions on Algorithms (TALG)
  • Year:
  • 2008

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Abstract

Contact graphs of isothetic rectangles unify many concepts from applications including VLSI and architectural design, computational geometry, and GIS. Minimizing the area of their corresponding rectangular layouts is a key problem. We study the area-optimization problem and show that it is NP-hard to find a minimum-area rectangular layout of a given contact graph. We present O(n)-time algorithms that construct O(n2)-area rectangular layouts for general contact graphs and O(n log n)-area rectangular layouts for trees. (For trees, this is an O(log n)-approximation algorithm.) We also present an infinite family of graphs (respectively, trees) that require Ω(n2) (respectively, Ω(n log n))area. We derive these results by presenting a new characterization of graphs that admit rectangular layouts, using the related concept of rectangular duals. A corollary to our results relates the class of graphs that admit rectangular layouts to rectangle-of-influence drawings.