arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.08179cs.DS
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编辑距离下的字符串清理:改进与推广

String Sanitization Under Edit Distance: Improved and Generalized

Takuya Mieno, Solon P. Pissis, Leen Stougie, Michelle Sweering

AI总结:

针对编辑距离下的字符串清理ETFS问题,提出多对数因子下最优的改进算法,并推广至可处理任意长度机密模式的AETFS问题,技术可启发相关领域研究。

摘要:

设$W$是字母表$Σ$上长度为$n$的字符串,$k$为正整数,$\u27a4S$是$W$的长度为$k$的子串构成的集合。ETFS问题要求构造字符串$X_{\u27a4ED}$,满足:(i) $\u27a4S$中没有字符串出现在$X_{\u27a4ED}$中;(ii) $Σ$上所有其他长度为$k$的子串的顺序(以及频率)在$W$和$X_{\u27a4ED}$中相同;(iii) $X_{\u27a4ED}$与$W$的编辑距离最小。当$W$代表个人数据、$\u27a4S$代表一组机密模式时,ETFS问题要求对$W$进行转换以同时保护隐私和保留效用[Bernardini等人,ECML PKDD 2019]。\nETFS可在$\u27a4O(n^2k)$时间内求解[Bernardini等人,CPM 2020]。该论文还证明,除非强指数时间假设(SETH)不成立,否则对任意$δ>0$,ETFS都无法在$\u27a4O(n^{2-δ})$时间内求解。我们的主要结果可总结如下:(i) 提出一种$\u27a4O(n^2\b2k)$时间的ETFS求解算法;(ii) 提出一种$\u27a4O(n^2\b2n)$时间的AETFS求解算法,AETFS是ETFS的推广形式,其中$\u27a4S$的元素可以是任意长度。因此,除非SETH不成立,我们的算法在多对数因子下是最优的。除字符串清理外,我们的技术还可能为正则表达式或上下文无关文法相关的其他问题的求解提供启发。

英文摘要:

Let $W$ be a string of length $n$ over an alphabet $Σ$, $k$ be a positive integer, and $\mathcal{S}$ be a set of length-$k$ substrings of $W$. The ETFS problem asks us to construct a string $X_{\mathrm{ED}}$ such that: (i) no string of $\mathcal{S}$ occurs in $X_{\mathrm{ED}}$; (ii) the order of all other length-$k$ substrings over $Σ$ (and thus the frequency) is the same in $W$ and in $X_{\mathrm{ED}}$; and (iii) $X_{\mathrm{ED}}$ has minimal edit distance to $W$. When $W$ represents an individual's data and $\mathcal{S}$ represents a set of confidential patterns, the ETFS problem asks for transforming $W$ to preserve its privacy and its utility [Bernardini et al., ECML PKDD 2019]. ETFS can be solved in $\mathcal{O}(n^2k)$ time [Bernardini et al., CPM 2020]. The same paper shows that ETFS cannot be solved in $\mathcal{O}(n^{2-δ})$ time, for any $δ>0$, unless the Strong Exponential Time Hypothesis (SETH) is false. Our main results can be summarized as follows: (i) an $\mathcal{O}(n^2\log^2k)$-time algorithm to solve ETFS; and (ii) an $\mathcal{O}(n^2\log^2n)$-time algorithm to solve AETFS, a generalization of ETFS in which the elements of $\mathcal{S}$ can have arbitrary lengths. Our algorithms are thus optimal up to polylogarithmic factors, unless SETH fails. Beyond string sanitization, our techniques may inspire solutions to other problems related to regular expressions or context-free grammars.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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