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arXiv 1603.08151cs.DScs.CGmath.CO
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二叉搜索树和矩形化

Binary search trees and rectangulations

László Kozma, Thatchaphol Saranurak

摘要:

我们重新审视经典的二叉搜索树(BST)中使用旋转搜索的问题,并提出了新的连接这个问题的一些几何和组合结构。特别是,我们表明,执行跟踪的BST服务的查询序列是在两个矩形之间的翻转序列密切对应。(矩形化是一种经过充分研究的组合对象,也称为马赛克平面图。)我们还重新解释小曼哈顿网络,一个已知的连接到BST问题的问题,在矩形翻转。我们对获得的几何模型进行进一步的变换,以获得BST问题的特别简单的视图,该视图类似于最短路径算法中的边缘松弛序列。我们的连接产生了新的结果和观察所有有关的结构。在这份草案中,我们提出了一些初步的调查结果。带旋转的BST是计算机科学中最基本和最彻底的研究对象之一,尽管如此,它们仍然提出了长期存在的开放问题,例如Sleator和Tarjan的动态最优性猜想(STOC 1983)。我们希望,本文提出的对应提供了一个新的视角,这个老问题,并带来新的工具,研究动态最优性。

英文摘要:

We revisit the classical problem of searching in a binary search tree (BST) using rotations, and present novel connections of this problem to a number of geometric and combinatorial structures. In particular, we show that the execution trace of a BST that serves a sequence of queries is in close correspondence with the flip-sequence between two rectangulations. (Rectangulations are well-studied combinatorial objects also known as mosaic floorplans.) We also reinterpret Small Manhattan Network, a problem with known connections to the BST problem, in terms of flips in rectangulations. We apply further transformations to the obtained geometric model, to arrive at a particularly simple view of the BST problem that resembles sequences of edge-relaxations in a shortest path algorithm. Our connections yield new results and observations for all structures concerned. In this draft we present some preliminary findings. BSTs with rotations are among the most fundamental and most thoroughly studied objects in computer science, nonetheless they pose long-standing open questions, such as the dynamic optimality conjecture of Sleator and Tarjan (STOC 1983). Our hope is that the correspondences presented in this paper provide a new perspective on this old problem and bring new tools to the study of dynamic optimality.

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