Grid drawings and the chromatic number

  • Authors:
  • Martin Balko

  • Affiliations:
  • Department of Applied Mathematics, Faculty of Mathematics and Physics, Charles University, Praha 1, Czech Republic

  • Venue:
  • GD'12 Proceedings of the 20th international conference on Graph Drawing
  • Year:
  • 2012

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Abstract

A grid drawing of a graph maps vertices to the grid ℤd and edges to line segments that avoid grid points representing other vertices. We show that a graph G is qd-colorable, d, q≥2, if and only if there is a grid drawing of G in ℤd in which no line segment intersects more than q grid points. This strengthens the result of D. Flores Pen̋aloza 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 Pen̋aloza and F. J. Zaragoza Martinez.