Algorithmica最新文献

筛选
英文 中文
Approximate and Randomized Algorithms for Computing a Second Hamiltonian Cycle 计算第二哈密顿周期的近似算法和随机算法
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-06-12 DOI: 10.1007/s00453-024-01238-z
Argyrios Deligkas, George B. Mertzios, Paul G. Spirakis, Viktor Zamaraev
{"title":"Approximate and Randomized Algorithms for Computing a Second Hamiltonian Cycle","authors":"Argyrios Deligkas,&nbsp;George B. Mertzios,&nbsp;Paul G. Spirakis,&nbsp;Viktor Zamaraev","doi":"10.1007/s00453-024-01238-z","DOIUrl":"10.1007/s00453-024-01238-z","url":null,"abstract":"<div><p>In this paper we consider the following problem: Given a Hamiltonian graph <i>G</i>, and a Hamiltonian cycle <i>C</i> of <i>G</i>, can we compute a second Hamiltonian cycle <span>(C^{prime } ne C)</span> of <i>G</i>, and if yes, how quickly? If the input graph <i>G</i> satisfies certain conditions (e.g. if every vertex of <i>G</i> is odd, or if the minimum degree is large enough), it is known that such a second Hamiltonian cycle always exists. Despite substantial efforts, no subexponential-time algorithm is known for this problem. In this paper we relax the problem of computing a second Hamiltonian cycle in two ways. First, we consider <i>approximating</i> the length of a second longest cycle on <i>n</i>-vertex graphs with minimum degree <span>(delta )</span> and maximum degree <span>(Delta )</span>. We provide a linear-time algorithm for computing a cycle <span>(C^{prime } ne C)</span> of length at least <span>(n-4alpha (sqrt{n}+2alpha )+8)</span>, where <span>(alpha = frac{Delta -2}{delta -2})</span>. This results provides a constructive proof of a recent result by Girão, Kittipassorn, and Narayanan in the regime of <span>(frac{Delta }{delta } = o(sqrt{n}))</span>. Our second relaxation of the problem is probabilistic. We propose a randomized algorithm which computes a second Hamiltonian cycle <i>with high probability</i>, given that the input graph <i>G</i> has a large enough minimum degree. More specifically, we prove that for every <span>(0&lt;ple 0.02)</span>, if the minimum degree of <i>G</i> is at least <span>(frac{8}{p} log sqrt{8}n + 4)</span>, then a second Hamiltonian cycle can be computed with probability at least <span>(1 - frac{1}{n}left( frac{50}{p^4} + 1 right) )</span> in <span>(poly(n) cdot 2^{4pn})</span> time. This result implies that, when the minimum degree <span>(delta )</span> is sufficiently large, we can compute with high probability a second Hamiltonian cycle faster than any known deterministic algorithm. In particular, when <span>(delta = omega (log n))</span>, our probabilistic algorithm works in <span>(2^{o(n)})</span> time.</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 9","pages":"2766 - 2785"},"PeriodicalIF":0.9,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00453-024-01238-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141351753","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}
引用次数: 0
Online Geometric Covering and Piercing 在线几何图形覆盖和穿孔
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-06-03 DOI: 10.1007/s00453-024-01244-1
Minati De, Saksham Jain, Sarat Varma Kallepalli, Satyam Singh
{"title":"Online Geometric Covering and Piercing","authors":"Minati De,&nbsp;Saksham Jain,&nbsp;Sarat Varma Kallepalli,&nbsp;Satyam Singh","doi":"10.1007/s00453-024-01244-1","DOIUrl":"10.1007/s00453-024-01244-1","url":null,"abstract":"<div><p>We consider the online version of the piercing set problem, where geometric objects arrive one by one, and the online algorithm must maintain a valid piercing set for the already arrived objects by making irrevocable decisions. It is easy to observe that any deterministic algorithm solving this problem for intervals in <span>(mathbb {R})</span> has a competitive ratio of at least <span>(Omega (n))</span>. This paper considers the piercing set problem for similarly sized objects. We propose a deterministic online algorithm for similarly sized fat objects in <span>(mathbb {R}^d)</span>. For homothetic hypercubes in <span>(mathbb {R}^d)</span> with side length in the range [1, <i>k</i>], we propose a deterministic algorithm having a competitive ratio of at most <span>(3^dlceil log _2 krceil +2^d)</span>. In the end, we show deterministic lower bounds of the competitive ratio for similarly sized <span>(alpha )</span>-fat objects in <span>(mathbb {R}^2)</span> and homothetic hypercubes in <span>(mathbb {R}^d)</span>. Note that piercing translated copies of a convex object is equivalent to the unit covering problem, which is well-studied in the online setup. Surprisingly, no upper bound of the competitive ratio was known for the unit covering problem when the corresponding object is anything other than a ball or a hypercube. Our result yields an upper bound of the competitive ratio for the unit covering problem when the corresponding object is any convex object in <span>(mathbb {R}^d)</span>.</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 9","pages":"2739 - 2765"},"PeriodicalIF":0.9,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141255935","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}
引用次数: 0
Slim Tree-Cut Width 纤细的树形切割宽度
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-06-01 DOI: 10.1007/s00453-024-01241-4
Robert Ganian, Viktoriia Korchemna
{"title":"Slim Tree-Cut Width","authors":"Robert Ganian,&nbsp;Viktoriia Korchemna","doi":"10.1007/s00453-024-01241-4","DOIUrl":"10.1007/s00453-024-01241-4","url":null,"abstract":"<div><p>Tree-cut width is a parameter that has been introduced as an attempt to obtain an analogue of treewidth for edge cuts. Unfortunately, in spite of its desirable structural properties, it turned out that tree-cut width falls short as an edge-cut based alternative to treewidth in algorithmic aspects. This has led to the very recent introduction of a simple edge-based parameter called edge-cut width [WG 2022], which has precisely the algorithmic applications one would expect from an analogue of treewidth for edge cuts, but does not have the desired structural properties. In this paper, we study a variant of tree-cut width obtained by changing the threshold for so-called thin nodes in tree-cut decompositions from 2 to 1. We show that this “slim tree-cut width” satisfies all the requirements of an edge-cut based analogue of treewidth, both structural and algorithmic, while being less restrictive than edge-cut width. Our results also include an alternative characterization of slim tree-cut width via an easy-to-use spanning-tree decomposition akin to the one used for edge-cut width, a characterization of slim tree-cut width in terms of forbidden immersions as well as approximation algorithm for computing the parameter.\u0000</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2714 - 2738"},"PeriodicalIF":0.9,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00453-024-01241-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141189002","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}
引用次数: 0
Approximating Long Cycle Above Dirac’s Guarantee 逼近狄拉克保证之上的长周期
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-05-30 DOI: 10.1007/s00453-024-01240-5
Fedor V. Fomin, Petr A. Golovach, Danil Sagunov, Kirill Simonov
{"title":"Approximating Long Cycle Above Dirac’s Guarantee","authors":"Fedor V. Fomin,&nbsp;Petr A. Golovach,&nbsp;Danil Sagunov,&nbsp;Kirill Simonov","doi":"10.1007/s00453-024-01240-5","DOIUrl":"10.1007/s00453-024-01240-5","url":null,"abstract":"<div><p>Parameterization above (or below) a guarantee is a successful concept in parameterized algorithms. The idea is that many computational problems admit “natural” guarantees bringing to algorithmic questions whether a better solution (above the guarantee) could be obtained efficiently. For example, for every boolean CNF formula on <i>m</i> clauses, there is an assignment that satisfies at least <i>m</i>/2 clauses. How difficult is it to decide whether there is an assignment satisfying more than <span>(m/2 +k)</span> clauses? Or, if an <i>n</i>-vertex graph has a perfect matching, then its vertex cover is at least <i>n</i>/2. Is there a vertex cover of size at least <span>(n/2 +k)</span> for some <span>(kge 1)</span> and how difficult is it to find such a vertex cover? The above guarantee paradigm has led to several exciting discoveries in the areas of parameterized algorithms and kernelization. We argue that this paradigm could bring forth fresh perspectives on well-studied problems in approximation algorithms. Our example is the longest cycle problem. One of the oldest results in extremal combinatorics is the celebrated Dirac’s theorem from 1952. Dirac’s theorem provides the following guarantee on the length of the longest cycle: for every 2-connected <i>n</i>-vertex graph <i>G</i> with minimum degree <span>(delta (G)le n/2)</span>, the length of a longest cycle <i>L</i> is at least <span>(2delta (G))</span>. Thus the “essential” part in finding the longest cycle is in approximating the “offset” <span>(k = L - 2 delta (G))</span>. The main result of this paper is the above-guarantee approximation theorem for <i>k</i>. Informally, the theorem says that approximating the offset <i>k</i> is not harder than approximating the total length <i>L</i> of a cycle. In other words, for any (reasonably well-behaved) function <i>f</i>, a polynomial time algorithm constructing a cycle of length <i>f</i>(<i>L</i>) in an undirected graph with a cycle of length <i>L</i>, yields a polynomial time algorithm constructing a cycle of length <span>(2delta (G)+Omega (f(k)))</span>.</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2676 - 2713"},"PeriodicalIF":0.9,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00453-024-01240-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141189001","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}
引用次数: 0
New Algorithms for Steiner Tree Reoptimization 斯坦纳树再优化的新算法
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-05-29 DOI: 10.1007/s00453-024-01243-2
Davide Bilò
{"title":"New Algorithms for Steiner Tree Reoptimization","authors":"Davide Bilò","doi":"10.1007/s00453-024-01243-2","DOIUrl":"10.1007/s00453-024-01243-2","url":null,"abstract":"<div><p><i>Reoptimization</i> is a setting in which we are given a good approximate solution of an optimization problem instance and a local modification that slightly changes the instance. The main goal is that of finding a good approximate solution of the modified instance. We investigate one of the most studied scenarios in reoptimization known as <i>Steiner tree reoptimization</i>. Steiner tree reoptimization is a collection of strongly <span>(textsf {NP})</span>-hard optimization problems that are defined on top of the classical Steiner tree problem and for which several constant-factor approximation algorithms have been designed in the last decades. In this paper we improve upon all these results by developing a novel technique that allows us to design <i>polynomial-time approximation schemes</i>. Remarkably, prior to this paper, no approximation algorithm better than recomputing a solution from scratch was known for the elusive scenario in which the cost of a single edge decreases. Our results are best possible since none of the problems addressed in this paper admits a fully polynomial-time approximation scheme, unless <span>(textsf {P}=textsf {NP})</span></p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2652 - 2675"},"PeriodicalIF":0.9,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00453-024-01243-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141170110","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}
引用次数: 0
Approximation Algorithms for Covering Vertices by Long Paths 用长路径覆盖顶点的近似算法
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-05-28 DOI: 10.1007/s00453-024-01242-3
Mingyang Gong, Brett Edgar, Jing Fan, Guohui Lin, Eiji Miyano
{"title":"Approximation Algorithms for Covering Vertices by Long Paths","authors":"Mingyang Gong,&nbsp;Brett Edgar,&nbsp;Jing Fan,&nbsp;Guohui Lin,&nbsp;Eiji Miyano","doi":"10.1007/s00453-024-01242-3","DOIUrl":"10.1007/s00453-024-01242-3","url":null,"abstract":"<div><p>Given a graph, the general problem to cover the maximum number of vertices by a collection of vertex-disjoint long paths seems to escape from the literature. A path containing at least <i>k</i> vertices is considered long. When <span>(k le 3)</span>, the problem is polynomial time solvable; when <i>k</i> is the total number of vertices, the problem reduces to the Hamiltonian path problem, which is NP-complete. For a fixed <span>(k ge 4)</span>, the problem is NP-hard and the best known approximation algorithm for the weighted set packing problem implies a <i>k</i>-approximation algorithm. To the best of our knowledge, there is no approximation algorithm directly designed for the general problem; when <span>(k = 4)</span>, the problem admits a 4-approximation algorithm which was presented recently. We propose the first <span>((0.4394 k + O(1)))</span>-approximation algorithm for the general problem and an improved 2-approximation algorithm when <span>(k = 4)</span>. Both algorithms are based on local improvement, and their theoretical performance analyses are done via amortization and their practical performance is examined through simulation studies.\u0000</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2625 - 2651"},"PeriodicalIF":0.9,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141170080","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}
引用次数: 0
Parity Permutation Pattern Matching 奇偶校验模式匹配
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-05-22 DOI: 10.1007/s00453-024-01237-0
Virginia Ardévol Martínez, Florian Sikora, Stéphane Vialette
{"title":"Parity Permutation Pattern Matching","authors":"Virginia Ardévol Martínez,&nbsp;Florian Sikora,&nbsp;Stéphane Vialette","doi":"10.1007/s00453-024-01237-0","DOIUrl":"10.1007/s00453-024-01237-0","url":null,"abstract":"<div><p>Given two permutations, a pattern <span>(sigma )</span> and a text <span>(pi )</span>, <span>Parity Permutation Pattern Matching</span> asks whether there exists a parity and order preserving embedding of <span>(sigma )</span> into <span>(pi )</span>. While it is known that <span>Permutation Pattern Matching</span> is in <span>(textsc {FPT})</span>, we show that adding the parity constraint to the problem makes it <span>(textsc {W}[1])</span>-hard, even for alternating permutations or for 4321-avoiding patterns. However, the problem remains in <span>(textsc {FPT})</span> if <span>(pi )</span> avoids a fixed permutation, thanks to a recent meta-theorem on twin-width. On the other hand, as for the classical version, <span>Parity Permutation Pattern Matching</span> remains polynomial-time solvable when the pattern is separable, or if both permutations are 321-avoiding, but <span>NP</span>-hard if <span>(sigma )</span> is 321-avoiding and <span>(pi )</span> is 4321-avoiding.</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2605 - 2624"},"PeriodicalIF":0.9,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141153304","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}
引用次数: 0
Improved Approximation Algorithms by Generalizing the Primal-Dual Method Beyond Uncrossable Functions 超越不可交函数,通过推广原初-双重方法改进逼近算法
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-05-20 DOI: 10.1007/s00453-024-01235-2
Ishan Bansal, Joseph Cheriyan, Logan Grout, Sharat Ibrahimpur
{"title":"Improved Approximation Algorithms by Generalizing the Primal-Dual Method Beyond Uncrossable Functions","authors":"Ishan Bansal,&nbsp;Joseph Cheriyan,&nbsp;Logan Grout,&nbsp;Sharat Ibrahimpur","doi":"10.1007/s00453-024-01235-2","DOIUrl":"10.1007/s00453-024-01235-2","url":null,"abstract":"<div><p>We address long-standing open questions raised by Williamson, Goemans, Vazirani and Mihail pertaining to the design of approximation algorithms for problems in network design via the primal-dual method (Williamson et al. in Combinatorica 15(3):435–454, 1995. https://doi.org/10.1007/BF01299747). Williamson et al. prove an approximation ratio of two for connectivity augmentation problems where the connectivity requirements can be specified by uncrossable functions. They state: “Extending our algorithm to handle non-uncrossable functions remains a challenging open problem. The key feature of uncrossable functions is that there exists an optimal dual solution which is laminar ... A larger open issue is to explore further the power of the primal-dual approach for obtaining approximation algorithms for other combinatorial optimization problems.” Our main result proves that the primal-dual algorithm of Williamson et al. achieves an approximation ratio of <span>(16)</span> for a class of functions that generalizes the notion of an uncrossable function. There exist instances that can be handled by our methods where none of the optimal dual solutions has a laminar support. We present three applications of our main result to problems in the area of network design. (1)  A <span>(16)</span>-approximation algorithm for augmenting a family of small cuts of a graph <i>G</i>. The previous best approximation ratio was <span>(O(log {|V(G)|}))</span>. (2)  A <span>(16cdot {lceil k/u_{min} rceil })</span>-approximation algorithm for the Cap-<i>k</i>-ECSS problem which is as follows: Given an undirected graph <span>(G = (V,E))</span> with edge costs <span>(c in {mathbb {Q}}_{ge 0}^E)</span> and edge capacities <span>(u in {mathbb {Z}}_{ge 0}^E)</span>, find a minimum-cost subset of the edges <span>(Fsubseteq E)</span> such that the capacity of any cut in (<i>V</i>, <i>F</i>) is at least <i>k</i>; <span>(u_{min})</span> (respectively, <span>(u_{max})</span>) denotes the minimum (respectively, maximum) capacity of an edge in <i>E</i>, and w.l.o.g. <span>(u_{max} le k)</span>. The previous best approximation ratio was <span>(min (O(log {|V|}), k, 2u_{max}))</span>. (3)  A <span>(20)</span>-approximation algorithm for the model of (<i>p</i>, 2)-Flexible Graph Connectivity. The previous best approximation ratio was <span>(O(log {|V(G)|}))</span>, where <i>G</i> denotes the input graph.\u0000</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2575 - 2604"},"PeriodicalIF":0.9,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141153393","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}
引用次数: 0
Parameterized Approximation Algorithms and Lower Bounds for k-Center Clustering and Variants k 中心聚类及其变体的参数化近似算法和下限
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-05-13 DOI: 10.1007/s00453-024-01236-1
Sayan Bandyapadhyay, Zachary Friggstad, Ramin Mousavi
{"title":"Parameterized Approximation Algorithms and Lower Bounds for k-Center Clustering and Variants","authors":"Sayan Bandyapadhyay,&nbsp;Zachary Friggstad,&nbsp;Ramin Mousavi","doi":"10.1007/s00453-024-01236-1","DOIUrl":"10.1007/s00453-024-01236-1","url":null,"abstract":"<div><p><i>k</i>-center is one of the most popular clustering models. While it admits a simple 2-approximation in polynomial time in general metrics, the Euclidean version is NP-hard to approximate within a factor of 1.82, even in the plane, if one insists the dependence on <i>k</i> in the running time be polynomial. Without this restriction, a classic algorithm by Agarwal and Procopiuc [Algorithmica 2002] yields an <span>(O(nlog k)+(1/epsilon )^{O(2^dk^{1-1/d}log k)})</span>-time <span>((1+epsilon ))</span>-approximation for Euclidean <i>k</i>-center, where <i>d</i> is the dimension. We show for a closely related problem, <i>k</i>-supplier, the double-exponential dependence on dimension is unavoidable if one hopes to have a sub-linear dependence on <i>k</i> in the exponent. We also derive similar algorithmic results to the ones by Agarwal and Procopiuc for both <i>k</i>-center and <i>k</i>-supplier. We use a relatively new tool, called Voronoi separator, which makes our algorithms and analyses substantially simpler. Furthermore we consider a well-studied generalization of <i>k</i>-center, called Non-uniform <i>k</i>-center (NUkC), where we allow different radii clusters. NUkC is NP-hard to approximate within any factor, even in the Euclidean case. We design a <span>(2^{O(klog k)}n^2)</span> time 3-approximation for NUkC in general metrics, and a <span>(2^{O((klog k)/epsilon )}dn)</span> time <span>((1+epsilon ))</span>-approximation for Euclidean NUkC. The latter time bound matches the bound for <i>k</i>-center.\u0000</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2557 - 2574"},"PeriodicalIF":0.9,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140942241","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}
引用次数: 0
Sample-Based Distance-Approximation for Subsequence-Freeness 基于样本的无后续距离近似法
IF 0.9 4区 计算机科学
Algorithmica Pub Date : 2024-05-13 DOI: 10.1007/s00453-024-01233-4
Omer Cohen Sidon, Dana Ron
{"title":"Sample-Based Distance-Approximation for Subsequence-Freeness","authors":"Omer Cohen Sidon,&nbsp;Dana Ron","doi":"10.1007/s00453-024-01233-4","DOIUrl":"10.1007/s00453-024-01233-4","url":null,"abstract":"<div><p>In this work, we study the problem of approximating the distance to subsequence-freeness in the sample-based distribution-free model. For a given subsequence (word) <span>(w = w_1 ldots w_k)</span>, a sequence (text) <span>(T = t_1 ldots t_n)</span> is said to contain <i>w</i> if there exist indices <span>(1 le i_1&lt; cdots &lt; i_k le n)</span> such that <span>(t_{i_{j}} = w_j)</span> for every <span>(1 le j le k)</span>. Otherwise, <i>T</i> is <i>w</i>-free. Ron and Rosin (ACM Trans Comput Theory 14(4):1–31, 2022) showed that the number of samples both necessary and sufficient for one-sided error testing of subsequence-freeness in the sample-based distribution-free model is <span>(Theta (k/epsilon ))</span>. Denoting by <span>(Delta (T,w,p))</span> the distance of <i>T</i> to <i>w</i>-freeness under a distribution <span>(p:[n]rightarrow [0,1])</span>, we are interested in obtaining an estimate <span>(widehat{Delta })</span>, such that <span>(|widehat{Delta }- Delta (T,w,p)| le delta )</span> with probability at least 2/3, for a given error parameter <span>(delta )</span>. Our main result is a sample-based distribution-free algorithm whose sample complexity is <span>(tilde{O}(k^2/delta ^2))</span>. We first present an algorithm that works when the underlying distribution <i>p</i> is uniform, and then show how it can be modified to work for any (unknown) distribution <i>p</i>. We also show that a quadratic dependence on <span>(1/delta )</span> is necessary.</p></div>","PeriodicalId":50824,"journal":{"name":"Algorithmica","volume":"86 8","pages":"2519 - 2556"},"PeriodicalIF":0.9,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00453-024-01233-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140927540","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}
引用次数: 0
0
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
相关产品
×
本文献相关产品
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信