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arXiv 2103.09735cs.DScs.CG
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二维的几何背包问题的截断可分填充

On Guillotine Separable Packings for the Two-dimensional Geometric Knapsack Problem

Arindam Khan, Arnab Maiti, Amatya Sharma, Andreas Wiese

摘要:

在二维的【形】几何背包问题中,我们给出了一组n个轴向对齐的矩形项和一个轴向对齐的正方形背包。每个项目都有积分宽度,积分高度和相关的积分利润。我们的目标是找到一个(非重叠轴对齐)包装的最大利润子集的矩形到背包。在实践中,一个被充分研究和经常使用的约束是只允许可截断分离的填料,即,可以通过递归地应用一系列边到边的轴平行切割来获得填充中的每个矩形,所述切割不与解的任何项相交。本文研究了截断约束下的几何背包问题的近似算法。假设所有输入数值数据在n中多项式有界,我们给出了允许旋转90度和不允许旋转90度两种情况下的多项式时间(1 + ε)-近似算法.相比之下,这种设置的最著名的近似因子是3 + ε [Jansen-Zhang,SODA 2004],即使在所有项目具有相同利润的基数情况下。我们的主要技术贡献是一个结构引理,它表明任何一种截断填料都可以转化为另一种结构化截断填料,而且几乎可以获得相同的利润。在这种包装中,每个物品都完全包含在一个恒定数量的盒子和L形区域中,物品通过简单的贪婪例程放置在其中。特别是,我们提供了一个干净的充分条件时,这样的包装遵守断头台切割约束,这可能是有用的其他设置,这些约束。

英文摘要:

In two-dimensional geometric knapsack problem, we are given a set of n axis-aligned rectangular items and an axis-aligned square-shaped knapsack. Each item has integral width, integral height and an associated integral profit. The goal is to find a (non-overlapping axis-aligned) packing of a maximum profit subset of rectangles into the knapsack. A well-studied and frequently used constraint in practice is to allow only packings that are guillotine separable, i.e., every rectangle in the packing can be obtained by recursively applying a sequence of edge-to-edge axis-parallel cuts that do not intersect any item of the solution. In this paper we study approximation algorithms for the geometric knapsack problem under guillotine cut constraints. We present polynomial time (1 + ε)-approximation algorithms for the cases with and without allowing rotations by 90 degrees, assuming that all input numeric data are polynomially bounded in n. In comparison, the best-known approximation factor for this setting is 3 + ε [Jansen-Zhang, SODA 2004], even in the cardinality case where all items have the same profit. Our main technical contribution is a structural lemma which shows that any guillotine packing can be converted into another structured guillotine packing with almost the same profit. In this packing, each item is completely contained in one of a constant number of boxes and L-shaped regions, inside which the items are placed by a simple greedy routine. In particular, we provide a clean sufficient condition when such a packing obeys the guillotine cut constraints which might be useful for other settings where these constraints are imposed.

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