Acta Informatica最新文献

{"title":"Tight bounds for the sensitivity of CDAWGs with left-end edits","authors":"Hiroto Fujimaru,&nbsp;Yuto Nakashima,&nbsp;Shunsuke Inenaga","doi":"10.1007/s00236-025-00478-y","DOIUrl":"10.1007/s00236-025-00478-y","url":null,"abstract":"<div><p><i>Compact directed acyclic word graphs</i> (<i>CDAWGs</i>) (Blumer et al. in J ACM 34(3):578–595, 1987) are a fundamental data structure on strings with applications in text pattern searching, data compression, and pattern discovery. Intuitively, the CDAWG of a string <i>T</i> is obtained by merging isomorphic subtrees of the suffix tree (Weiner, in: Proceedings of the 14th annual symposium on switching and automata theory, pp 1–11, 1973) of the same string <i>T</i>, thus CDAWGs are a compact indexing structure. In this paper, we investigate the sensitivity of CDAWGs when a single character edit operation (insertion, deletion, or substitution) is performed at the left-end of the input string <i>T</i>, namely, we are interested in the worst-case increase in the size of the CDAWG after a left-end edit operation. We prove that if <span>(textsf{e})</span> is the number of edges of the CDAWG for string <i>T</i>, then the number of new edges added to the CDAWG after a left-end edit operation on <i>T</i> does not exceed <span>(textsf{e})</span>. Further, we present a matching lower bound on the sensitivity of CDAWGs for left-end insertions, and almost matching lower bounds for left-end deletions and substitutions. We then generalize our lower-bound instance for left-end insertions to <i>leftward online construction</i> of the CDAWG, and show that it requires <span>(Omega (n^2))</span> time for some string of length <i>n</i>.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improving LSH via tensorized random projection","authors":"Bhisham Dev Verma,&nbsp;Rameshwar Pratap","doi":"10.1007/s00236-025-00479-x","DOIUrl":"10.1007/s00236-025-00479-x","url":null,"abstract":"<div><p>Locality-sensitive hashing (LSH) is a fundamental algorithmic toolkit used by data scientists for approximate nearest neighbour search problems that have been used extensively in many large-scale data processing applications such as near-duplicate detection, nearest-neighbour search, clustering, etc. In this work, we aim to propose faster and space-efficient locality-sensitive hash functions for Euclidean distance and cosine similarity for tensor data. Typically, the naive approach for obtaining LSH for tensor data involves first reshaping the tensor into vectors, followed by applying existing LSH methods for vector data. However, this approach becomes impractical for higher-order tensors because the size of the reshaped vector becomes exponential in the order of the tensor. Consequently, the size of LSH’s parameters increases exponentially. To address this problem, we suggest two methods for LSH for Euclidean distance and cosine similarity, namely CP-E2LSH, TT-E2LSH, and CP-SRP, TT-SRP, respectively, building on CP and tensor train (TT) decompositions techniques. Our approaches are space-efficient and can be efficiently applied to low-rank CP or TT tensors. We provide a rigorous theoretical analysis of our proposal on their correctness and efficacy.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correction: Birkhoff-von Neumann quantum logic enriched with entanglement quantifiers: coincidence theorem and semantic consequence","authors":"Shengyang Zhong","doi":"10.1007/s00236-025-00477-z","DOIUrl":"10.1007/s00236-025-00477-z","url":null,"abstract":"","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143110144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Directed capacity-preserving subgraphs: hardness and exact polynomial algorithms","authors":"Markus Chimani,&nbsp;Max Ilsen","doi":"10.1007/s00236-024-00475-7","DOIUrl":"10.1007/s00236-024-00475-7","url":null,"abstract":"<div><p>We introduce and discuss the <span>Minimum Capacity-Preserving Subgraph (MCPS)</span> problem: given a directed graph with edge capacities <span>(textit{cap} )</span> and a retention ratio <span>(alpha in (0,1))</span>, find the smallest subgraph that, for each pair of vertices (<i>u</i>, <i>v</i>), preserves at least a fraction <span>(alpha )</span> of a maximum <i>u</i>-<i>v</i>-flow’s value. This problem originates from the practical setting of reducing the power consumption in a computer network: it models turning off as many links as possible, while retaining the ability to transmit at least <span>(alpha )</span> times the traffic compared to the original network. First we prove that <span>MCPS</span> is NP-hard already on a restricted set of directed acyclic graphs (DAGs) with unit edge capacities. Our reduction also shows that a closely related problem (which only considers the arguably most complicated core of the problem in the objective function) is NP-hard to approximate within a sublogarithmic factor already on DAGs. In terms of positive results, we present two algorithms that solve <span>MCPS</span> optimally on directed series-parallel graphs (DSPs): a simple linear-time algorithm for the special case of unit edge capacities and a cubic-time dynamic programming algorithm for the general case of non-uniform edge capacities. Further, we introduce the family of laminar series-parallel graphs (LSPs), a generalization of DSPs that also includes cyclic and very dense graphs. Their properties allow us to solve <span>MCPS</span> on LSPs by employing our DSP-algorithms as subroutines. In addition, we give a separate quadratic-time algorithm for <span>MCPS</span> on LSPs with unit edge capacities that also yields straightforward quadratic time algorithms for several related problems such as <span>Minimum Equivalent Digraph</span> and <span>Directed Hamiltonian Cycle</span> on LSPs.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-024-00475-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exact and parameterized algorithms for choosability.","authors":"Ivan Bliznets, Jesper Nederlof","doi":"10.1007/s00236-025-00492-0","DOIUrl":"https://doi.org/10.1007/s00236-025-00492-0","url":null,"abstract":"<p><p>In the Choosability problem (or list chromatic number problem), for a given graph <i>G</i>, we need to find the smallest <i>k</i> such that <i>G</i> admits a list coloring for any list assignment where all lists contain at least <i>k</i> colors. The problem is tightly connected with the well-studied Coloring and List Coloring problems. However, the knowledge of the complexity landscape for the Choosability problem is pretty scarce. Moreover, most of the known results only provide lower bounds for its computational complexity and do not provide ways to cope with the intractability. The main objective of our paper is to construct the first non-trivial exact exponential algorithms for the Choosability problem, and complete the picture with parameterized results. Specifically, we present the first single-exponential algorithm for the decision version of the problem with fixed <i>k</i>. This result answers an implicit question from Eppstein on a stackexchange thread discussing upper bounds on the union of lists assigned to vertices. We also present a [Formula: see text] time algorithm for the general Choosability problem. In the parameterized setting, we give a polynomial kernel for the problem parameterized by vertex cover, and algorithms that run in FPT time when parameterized by a size of a clique-modulator and by the dual parameterization [Formula: see text]. Additionally, we show that Choosability admits a significant running time improvement if it is parameterized by cutwidth in comparison with the parameterization by treewidth studied by Marx and Mitsou [ICALP'16]. On the negative side, we provide a lower bound parameterized by a size of a modulator to split graphs under assumption of the Exponential Time Hypothesis.</p>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 2","pages":"24"},"PeriodicalIF":0.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12125139/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144198053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fault-tolerance in distance-edge-monitoring sets","authors":"Chenxu Yang,&nbsp;Yaping Mao,&nbsp;Ralf Klasing,&nbsp;Gang Yang,&nbsp;Yuzhi Xiao,&nbsp;Xiaoyan Zhang","doi":"10.1007/s00236-024-00476-6","DOIUrl":"10.1007/s00236-024-00476-6","url":null,"abstract":"<div><p>Let <i>G</i> be a connected graph. For an edge <span>(e=xy in E(G))</span>, <i>e</i> is monitored by a vertex <i>v</i> if <span>(d_G(v, y)ne d_{G-e}(v, y))</span> or <span>(d_G(v, x)ne d_{G-e}(v, x))</span>. A set <i>M</i> of vertices of a graph <i>G</i> is distance-edge-monitoring (DEM for short) set if every edge <i>e</i> of <i>G</i> is monitored by some vertex of <i>M</i>. A DEM set <i>X</i> for a graph <i>G</i> is called fault-tolerant DEM set if <span>(Xsetminus {v})</span> is also DEM set for each <i>v</i> in <i>X</i>. Denote <span>(operatorname {dem}(G))</span> and <span>(operatorname {Fdem}(G))</span> the smallest size of DEM set and fault-tolerant DEM sets, respectively. In this paper, we first study the relation between <span>(operatorname {Fdem}(G))</span> and <span>(operatorname {dem}(G))</span> for a graph <i>G</i>. Next, we show that <span>(2 le operatorname {Fdem}(G) le n)</span> for any graph <i>G</i> with order <i>n</i>. Furthermore, the extremal graphs attaining lower and upper bounds are characterized. In the end, the exact values for some networks are given. Furthermore, it is shown that for <span>(2le s&lt;tle n)</span>, there exists a graph <i>G</i> of order <i>n</i> such that <span>(operatorname {dem}(G)=s)</span> and <span>(operatorname {Fdem}(G)=t)</span>.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142889663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dense non-binary Fibonacci codes","authors":"Shmuel T. Klein,&nbsp;Dana Shapira","doi":"10.1007/s00236-024-00473-9","DOIUrl":"10.1007/s00236-024-00473-9","url":null,"abstract":"<div><p>The current study advances prior research on non-binary Fibonacci codes by introducing new families of universal codes. These codes demonstrate the advantage of accommodating a larger number of codewords for sufficiently large lengths. They retain the properties of instantaneous decipherability and robustness against transmission errors. This work presents these dense codes as a promising alternative for compressing extensive lists of very large integers, commonly encountered in cryptographic applications. \u0000</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142844846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Birkhoff-von Neumann quantum logic as an assertion language for quantum programs","authors":"Shengyang Zhong","doi":"10.1007/s00236-024-00472-w","DOIUrl":"10.1007/s00236-024-00472-w","url":null,"abstract":"<div><p>In this paper, we investigate a slightly simplified version of Birkhoff–von Neumann quantum logic enriched with entanglement quantifiers which is proposed in Ying (Birkhoff–von Neumann quantum logic as an assertion language for quantum programs, 2022. arXiv:2205.01959). The main result is a coincidence theorem, which says that every formula is interpreted by a closed subspace in the Hilbert space corresponding to the free variables of the formula. We also prove that many instances of semantic consequence, which are used in the proof of the prenex normal form theorem in first-order logic, also hold in this logic. The technical work is about the interplay among the three operations on density operators, namely, tensor product, support and partial trace.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142811099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parameterized algorithms for the Steiner arborescence problem on a hypercube","authors":"Sugyani Mahapatra,&nbsp;Manikandan Narayanan,&nbsp;N. S. Narayanaswamy","doi":"10.1007/s00236-024-00474-8","DOIUrl":"10.1007/s00236-024-00474-8","url":null,"abstract":"<div><p>Motivated by a phylogeny reconstruction problem in evolutionary biology, we study the minimum Steiner arborescence problem on directed hypercubes (<span>MSA</span>-<span>DH</span>). Given <i>m</i>, representing the directed hypercube <span>(vec {Q}_m)</span>, and a set of terminals <span>(R)</span>, the problem asks to find a Steiner arborescence that spans <span>(R)</span> with minimum cost. As <span>(m)</span> implicitly represents <span>(vec {Q}_{m})</span> comprising <span>(2^{m})</span> vertices, the running time analyses of traditional Steiner tree algorithms on general graphs does not give a clear understanding of the actual complexity of this problem. We present algorithms that exploit the structure of the hypercube and run in <span>FPT</span> time. We explore the <span>MSA</span>-<span>DH</span> problem on three natural parameters—<span>(|R|)</span>, and two above-guarantee parameters, number of Steiner nodes <i>p</i> and penalty <i>q</i> (defined as the extra cost above <i>m</i> incurred by the solution). For above-guarantee parameters, the parameterized <span>MSA</span>-<span>DH</span> problem take <span>(p ge 0)</span> or <span>(qge 0)</span> as input, and outputs a Steiner arborescence with at most <span>(|R|+ p - 1)</span> or <span>(m+ q)</span> edges respectively. We present the following results (<span>(tilde{{mathcal {O}}})</span> hides the polynomial factors): </p><ol>\u0000 <li>\u0000 <span>1.</span>\u0000 \u0000 <p>An exact algorithm that runs in <span>(tilde{{mathcal {O}}}(3^{|R|}))</span> time.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>2.</span>\u0000 \u0000 <p>A randomized algorithm that runs in <span>(tilde{{mathcal {O}}}(9^q))</span> time with success probability <span>(ge 4^{-q})</span>.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>3.</span>\u0000 \u0000 <p>An exact algorithm that runs in <span>(tilde{{mathcal {O}}}(36^q))</span> time.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>4.</span>\u0000 \u0000 <p>A <span>((1+q))</span>-approximation algorithm that runs in <span>(tilde{{mathcal {O}}}(1.25284^q))</span> time.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>5.</span>\u0000 \u0000 <p>An <span>({mathcal {O}}left( pell _{textrm{max}}right) )</span>-additive approximation algorithm that runs in <span>(tilde{{mathcal {O}}}(ell _{textrm{max}}^{p+2}))</span> time, where <span>(ell _{textrm{max}})</span> is the maximum distance of any terminal from the root.</p>\u0000 \u0000 </li>\u0000 </ol></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2024-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142789334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A sharp lower bound on the independence number of k-regular connected hypergraphs with rank R","authors":"Zhongzheng Tang,&nbsp;Haoyang Zou,&nbsp;Zhuo Diao","doi":"10.1007/s00236-024-00468-6","DOIUrl":"10.1007/s00236-024-00468-6","url":null,"abstract":"<div><p>Let <i>H</i>(<i>V</i>, <i>E</i>) be a <i>k</i>-regular connected hypergraph with rank <i>R</i> on <i>n</i> vertices and <i>m</i> edges. A set of vertices <span>(Ssubseteq V)</span> is an independent set if every two vertices in <i>S</i> are not adjacent. The independence number is the maximum cardinality of an independent set, denoted by <span>(alpha (H))</span>. In this paper, we prove the following inequality: <span>(alpha (H)ge frac{m-(k-2)n-1}{R})</span>, and the equality holds if and only if <i>H</i> is a hypertree with <i>R</i>-perfect matching. Based on the proofs, some combinatorial algorithms on the independence number are designed.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142753999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}