Reprint of: Grid representations and the chromatic number

  • Authors:
  • Martin Balko

  • Affiliations:
  • -

  • Venue:
  • Computational Geometry: Theory and Applications
  • Year:
  • 2014

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Abstract

A grid drawing of a graph maps vertices to the grid Z^d and edges to line segments that avoid grid points representing other vertices. We show that a graph G is q^d-colorable, d, q=2, if and only if there is a grid drawing of G in Z^d in which no line segment intersects more than q grid points. This strengthens the result of D. Flores Pen@?aloza and F.J. Zaragoza Martinez. Second, we study grid drawings with a bounded number of columns, introducing some new NP-complete problems. Finally, we show that any planar graph has a planar grid drawing where every line segment contains exactly two grid points. This result proves conjectures asked by D. Flores Pen@?aloza and F.J. Zaragoza Martinez.