Unit disk graphs are graphs that have a unit disk intersection representation (UDR). In the recognition problem the objective is to decide whether a given graph is a unit disk graph, which is known to be NP-hard, even for planar graphs. In this work, we show that the recognition of unit disk graphs remains NP-hard for outerplanar graphs and for embedded trees. We also show that given a caterpillar graph, we can decide in linear time whether it is a unit disk graph.
翻译:单位磁盘图是具有单位磁盘交叉图解(UDR)的图形。在识别问题中,目标在于确定某一图表是否为单位磁盘图,即使对于平面图来说,也已知为NP-硬盘图。在这项工作中,我们显示,对于外部平面图和嵌入的树来说,对单位磁盘图的识别仍然是NP-硬体。我们还显示,根据毛虫图,我们可以在线性时间里决定它是否为单位磁盘图。