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Ranking and Unranking t-ary Trees in a Gray-Code Order

机译:按格雷码顺序对三叉树进行排名和取消排名

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摘要

A t-ary tree is a rooted tree such that every internal node has exactly t disjoint subtrees. Recently, a concise representation called right-distance sequences (RD-sequences) was introduced to represent t-ary trees and their generalization called non-regular trees. In particular, a loopless algorithm has been proposed by Wu et al. ((2010) Loopless generation of non-regular trees with a prescribed branching sequence. Comput.)., 53,661-666) for generating non-regular trees (and thus of t-ary trees) encoded by RD-sequences in a Gray-code order. In this paper, based on such a Gray-code order, we present efficient ranking and unranking algorithms of t-ary trees with n internal nodes. The time complexity and space requirement in both algorithms are O(max{n~2, tn}) and O(tn), respectively. As a byproduct, we have an improvement on ranking and unranking t-ary trees encoded by z-sequences in a Gray-code order.
机译:三元树是一棵根树,因此每个内部节点都具有t个不相交的子树。最近,一种称为右距离序列(RD-equences)的简明表示法被引入来表示三进制树,它们的泛化称为非规则树。特别是,Wu等人提出了一种无环算法。 ((2010)使用规定的分支序列无循环生成非规则树。计算,。,53,661-666),用于生成由Gray序列中的RD序列编码的非规则树(以及t级树)。代码顺序。在本文中,基于这样的格雷码顺序,我们提出了具有n个内部节点的三进制树的有效排序和不排序算法。两种算法的时间复杂度和空间要求分别为O(max {n〜2,tn})和O(tn)。作为副产品,我们对按格雷码顺序对由z序列编码的三进制树进行排序和不排序进行了改进。

著录项

  • 来源
    《The Computer journal》 |2013年第11期|1388-1395|共8页
  • 作者单位

    Department of Industrial Management, Lunghwa University of Science and Technology, Taoyuan, Taiwan, ROC;

    Institute of Information and Decision Sciences, National Taipei College of Business, Taipei, Taiwan, ROC;

    Institute of Information and Decision Sciences, National Taipei College of Business, Taipei, Taiwan, ROC;

    Department of Humanity and Social Science, National Taiwan Normal University, Taipei, Taiwan, ROC;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    ranking algorithms; unranking algorithms; lexicographic order; Gray-code order; t-ary trees;

    机译:排名算法;排序算法;字典顺序;格雷码顺序;三元树;

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