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Upward Three-Dimensional Grid Drawings of Graphs

机译:图的向上三维网格图

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A three-dimensional grid drawing of a graph is a placement of the vertices at distinct points with integer coordinates, such that the straight line segments representing the edges do not cross. Our aim is to produce three-dimensional grid drawings with small bounding box volume. Our first main result is that every n-vertex graph with bounded degeneracy has a three-dimensional grid drawing with O (n~(3/2)) volume. This is the largest known class of graphs that have such drawings. A three-dimensional grid drawing of a directed acyclic graph (dag) is upward if every arc points up in the z-direction, We prove that every dag has an upward three-dimensional grid drawing with O (n~3) volume, which is tight for the complete dag. The previous best upper bound was O (n~4). Our main result concerning upward drawings is that every c-colourable dag (c constant) has an upward three-dimensional grid drawing with O (n~2) volume. This result matches the bound in the undirected case, and improves the best known bound from O (n~3) for many classes of dags, including planar, series parallel, and outerplanar. Improved bounds are also obtained for tree dags. We prove a strong relationship between upward three-dimensional grid drawings, upward track layouts, and upward queue layouts. Finally, we study upward three-dimensional grid drawings with bends in the edges.
机译:图形的三维网格图是将顶点放置在具有整数坐标的不同点上,这样代表边缘的直线段不会交叉。我们的目标是制作具有较小边界框体积的三维网格图。我们的第一个主要结果是每个有界退化的n个顶点图都有一个三维网格图,其体积为O(n〜(3/2))。这是具有此类绘图的最大已知图形类别。如果每个圆弧都指向z方向,则有向无环图(dag)的三维网格图是向上的。我们证明每个dag都有一个向上的三维网格图,其体积为O(n〜3),其中对于完整的dag是紧的。先前的最佳上限是O(n〜4)。我们有关向上绘制的主要结果是,每个c着色dag(c常数)都有一个向上的三维网格图,其体积为O(n〜2)。此结果与无向情况下的边界匹配,并且针对许多类别的dag,包括平面,串联平行和外平面,从O(n〜3)改善了最著名的边界。对于树dags也获得了改进的边界。我们证明了向上的三维网格图形,向上的轨道布局和向上的队列布局之间的密切关系。最后,我们研究了边缘弯曲的向上三维网格图。

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