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arXiv 1507.04046cs.DS
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树的距离标号方案

Distance labeling schemes for trees

Stephen Alstrup, Inge Li Gørtz, Esben Bistrup Halvorsen, Ely Porat

摘要:

我们考虑树的距离标记方案:给定一棵带有$n$节点的树,用二进制字符串标记节点,这样,给定任何两个节点的标签,人们可以通过只看标签来确定树中两个节点之间的距离。一个下界由加沃耶等。等(J. Alg. 2004)和Peleg(J. Graph Theory 2000)的上限建立了标签必须使用$Θ(\log^2 n)$位\footnote{Throughout this paper we use $\log$ for $\log_2$.}。加沃耶等等人(ESA 2001)表明,对于非常小近似拉伸,标签使用$Θ(\log n \log \log n)$位。其他几篇论文研究了各种变体,例如树中的小距离(Alstrup et.例如,SODA'03)。我们改进了已知的精确距离标记的上限和下限,表明$\frac{1}{4} \log^2 n$位是必要的,$\frac{1}{2} \log^2 n$位是足够的。我们也给($1+ε$)拉伸标记计划使用$Θ(\log n)$位恒定的$ε>0$。($1+ε$)-拉伸标记计划与多对数标签的大小之前已经建立了由Talwar(STOC 2004)的双维图。此外,我们提出了匹配的上限和下限的距离标记毛虫,标签必须有大小$2\log n - Θ(\log\log n)$。对于$k$节点和边缘权重在$[1,n]$的简单路径,我们表明,标签必须有大小$\frac{k-1}{k}\log n+Θ(\log k)$。

英文摘要:

We consider distance labeling schemes for trees: given a tree with $n$ nodes, label the nodes with binary strings such that, given the labels of any two nodes, one can determine, by looking only at the labels, the distance in the tree between the two nodes. A lower bound by Gavoille et. al. (J. Alg. 2004) and an upper bound by Peleg (J. Graph Theory 2000) establish that labels must use $Θ(\log^2 n)$ bits\footnote{Throughout this paper we use $\log$ for $\log_2$.}. Gavoille et. al. (ESA 2001) show that for very small approximate stretch, labels use $Θ(\log n \log \log n)$ bits. Several other papers investigate various variants such as, for example, small distances in trees (Alstrup et. al., SODA'03). We improve the known upper and lower bounds of exact distance labeling by showing that $\frac{1}{4} \log^2 n$ bits are needed and that $\frac{1}{2} \log^2 n$ bits are sufficient. We also give ($1+ε$)-stretch labeling schemes using $Θ(\log n)$ bits for constant $ε>0$. ($1+ε$)-stretch labeling schemes with polylogarithmic label size have previously been established for doubling dimension graphs by Talwar (STOC 2004). In addition, we present matching upper and lower bounds for distance labeling for caterpillars, showing that labels must have size $2\log n - Θ(\log\log n)$. For simple paths with $k$ nodes and edge weights in $[1,n]$, we show that labels must have size $\frac{k-1}{k}\log n+Θ(\log k)$.

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