Journal of Computer and System Sciences最新文献_第8页

An FPT algorithm for timeline cover 时间线覆盖的FPT算法

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-12-01 Epub Date: 2025-05-22 DOI: 10.1016/j.jcss.2025.103679

Riccardo Dondi , Manuel Lafond

引用次数: 0

Finding diameter-reducing shortcuts in trees 在树上寻找减少直径的捷径

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-11-01 Epub Date: 2025-04-23 DOI: 10.1016/j.jcss.2025.103658

Davide Bilò , Luciano Gualà , Stefano Leucci , Luca Pepè Sciarria

{"title":"Finding diameter-reducing shortcuts in trees","authors":"Davide Bilò , Luciano Gualà , Stefano Leucci , Luca Pepè Sciarria","doi":"10.1016/j.jcss.2025.103658","DOIUrl":"10.1016/j.jcss.2025.103658","url":null,"abstract":"<div><div>In the <em>k-Diameter-Optimally Augmenting Tree Problem</em> we are given a tree <em>T</em> of <em>n</em> vertices embedded in an unknown <em>metric</em> space. An oracle can report the cost of any edge in constant time, and we want to augment <em>T</em> with <em>k</em> shortcuts to minimize the resulting diameter. When <span><math><mi>k</mi><mo>=</mo><mn>1</mn></math></span>, <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>log</mi><mo>⁡</mo><mi>n</mi><mo>)</mo></math></span>-time algorithms exist for paths and trees. We show that <span><math><mi>o</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span> queries cannot provide a better than 10/9-approximation for trees when <span><math><mi>k</mi><mo>≥</mo><mn>3</mn></math></span>. For any constant <span><math><mi>ε</mi><mo>></mo><mn>0</mn></math></span>, we design a linear-time <span><math><mo>(</mo><mn>1</mn><mo>+</mo><mi>ε</mi><mo>)</mo></math></span>-approximation algorithm for paths when <span><math><mi>k</mi><mo>=</mo><mi>o</mi><mo>(</mo><msqrt><mrow><mi>log</mi><mo>⁡</mo><mi>n</mi></mrow></msqrt><mo>)</mo></math></span>, thus establishing a dichotomy between paths and trees for <span><math><mi>k</mi><mo>≥</mo><mn>3</mn></math></span>. Our algorithm employs an ad-hoc data structure, which we also use in a linear-time 4-approximation algorithm for trees, and to compute the diameter of (possibly non-metric) graphs with <span><math><mi>n</mi><mo>+</mo><mi>k</mi><mo>−</mo><mn>1</mn></math></span> edges in time <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>k</mi><mi>log</mi><mo>⁡</mo><mi>n</mi><mo>)</mo></math></span>.</div></div>","PeriodicalId":50224,"journal":{"name":"Journal of Computer and System Sciences","volume":"153 ","pages":"Article 103658"},"PeriodicalIF":1.1,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143879465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Near-optimal dispersion on arbitrary anonymous graphs 任意匿名图上的近最优色散

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-09-01 Epub Date: 2025-03-22 DOI: 10.1016/j.jcss.2025.103656

Ajay D. Kshemkalyani , Gokarna Sharma

{"title":"Near-optimal dispersion on arbitrary anonymous graphs","authors":"Ajay D. Kshemkalyani , Gokarna Sharma","doi":"10.1016/j.jcss.2025.103656","DOIUrl":"10.1016/j.jcss.2025.103656","url":null,"abstract":"<div><div>Given an undirected, anonymous, port-labeled graph of <em>n</em> memory-less nodes, <em>m</em> edges, and degree Δ, we consider the problem of dispersing <span><math><mi>k</mi><mo>≤</mo><mi>n</mi></math></span> robots (or tokens) positioned initially arbitrarily on the nodes of the graph to exactly <em>k</em> different nodes, one on each node. The objective is to simultaneously minimize time and memory requirement at each robot. The best previously known algorithm solves this problem in <span><math><mi>O</mi><mo>(</mo><mi>min</mi><mo>⁡</mo><mo>{</mo><mi>m</mi><mo>,</mo><mi>k</mi><mi>Δ</mi><mo>}</mo><mo>⋅</mo><mi>log</mi><mo>⁡</mo><mi>ℓ</mi><mo>)</mo></math></span> time storing <span><math><mi>O</mi><mo>(</mo><mi>log</mi><mo>⁡</mo><mo>(</mo><mi>k</mi><mo>+</mo><mi>Δ</mi><mo>)</mo><mo>)</mo></math></span> bits at each robot, where <span><math><mi>ℓ</mi><mo>≤</mo><mi>k</mi><mo>/</mo><mn>2</mn></math></span> is the number of nodes with multiple robots positioned on them in the initial configuration. In this paper, we present a novel multi-source DFS traversal algorithm solving this problem in <span><math><mi>O</mi><mo>(</mo><mi>min</mi><mo>⁡</mo><mo>{</mo><mi>m</mi><mo>,</mo><mi>k</mi><mi>Δ</mi><mo>}</mo><mo>)</mo></math></span> time with <span><math><mi>O</mi><mo>(</mo><mi>log</mi><mo>⁡</mo><mo>(</mo><mi>k</mi><mo>+</mo><mi>Δ</mi><mo>)</mo><mo>)</mo></math></span> bits at each robot. The memory complexity of our algorithm is already asymptotically optimal and the time complexity is asymptotically optimal for the graphs of constant degree <span><math><mi>Δ</mi><mo>=</mo><mi>O</mi><mo>(</mo><mn>1</mn><mo>)</mo></math></span>. The result holds in both synchronous and asynchronous settings.</div></div>","PeriodicalId":50224,"journal":{"name":"Journal of Computer and System Sciences","volume":"152 ","pages":"Article 103656"},"PeriodicalIF":1.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143739196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Bounding the number of reticulation events for displaying multiple trees in a phylogenetic network 限制在系统发育网络中显示多个树的网状事件的数量

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-09-01 Epub Date: 2025-03-20 DOI: 10.1016/j.jcss.2025.103657

Yufeng Wu , Louxin Zhang

引用次数: 0

A linear delay algorithm in SD set system and its application to subgraph enumeration SD集合系统中的一种线性延迟算法及其在子图枚举中的应用

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-09-01 Epub Date: 2025-02-21 DOI: 10.1016/j.jcss.2025.103637

Takumi Tada, Kazuya Haraguchi

{"title":"A linear delay algorithm in SD set system and its application to subgraph enumeration","authors":"Takumi Tada, Kazuya Haraguchi","doi":"10.1016/j.jcss.2025.103637","DOIUrl":"10.1016/j.jcss.2025.103637","url":null,"abstract":"<div><div>For a set system <span><math><mo>(</mo><mi>V</mi><mo>,</mo><mi>C</mi><mo>⊆</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>V</mi></mrow></msup><mo>)</mo></math></span>, we call each <span><math><mi>C</mi><mo>∈</mo><mi>C</mi></math></span> a component. A nonempty subset <span><math><mi>Y</mi><mo>⊊</mo><mi>C</mi></math></span> is a removable set (RS) of <em>C</em> if <span><math><mi>C</mi><mo>∖</mo><mi>Y</mi></math></span> is a component. We say that a set system has subset-disjoint (SD) property if, for any two components <span><math><mi>C</mi><mo>,</mo><msup><mrow><mi>C</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span> with <span><math><msup><mrow><mi>C</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>⊊</mo><mi>C</mi></math></span>, every minimal RS <em>Y</em> of <em>C</em> satisfies either <span><math><mi>Y</mi><mo>⊆</mo><msup><mrow><mi>C</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span> or <span><math><mi>Y</mi><mo>∩</mo><msup><mrow><mi>C</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>=</mo><mo>∅</mo></math></span>. Assuming that an SD set system is implicitly given by an oracle that returns a minimal RS of a component, we provide an algorithm that enumerates all components in linear time/space with respect to <span><math><mo>|</mo><mi>V</mi><mo>|</mo></math></span> and oracle running time/space. We then extend this algorithm to linear-delay enumeration of all 2-edge-connected (or 2-vertex-connected) induced subgraphs in an undirected graph and of all strongly connected subgraphs in a digraph.</div></div>","PeriodicalId":50224,"journal":{"name":"Journal of Computer and System Sciences","volume":"152 ","pages":"Article 103637"},"PeriodicalIF":1.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143509232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Instability of backoff protocols with arbitrary arrival rates 任意到达率下退避方案的不稳定性

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-09-01 Epub Date: 2025-03-04 DOI: 10.1016/j.jcss.2025.103638

Leslie Ann Goldberg, John Lapinskas

引用次数: 0

Reconstructing semi-directed level-1 networks using few quarnets 利用少四元重构半有向一级网络

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-09-01 Epub Date: 2025-03-19 DOI: 10.1016/j.jcss.2025.103655

Martin Frohn , Niels Holtgrefe , Leo van Iersel , Mark Jones , Steven Kelk

{"title":"Reconstructing semi-directed level-1 networks using few quarnets","authors":"Martin Frohn , Niels Holtgrefe , Leo van Iersel , Mark Jones , Steven Kelk","doi":"10.1016/j.jcss.2025.103655","DOIUrl":"10.1016/j.jcss.2025.103655","url":null,"abstract":"<div><div>Semi-directed networks are partially directed graphs that model evolution where the directed edges represent reticulate evolutionary events. We present an algorithm that reconstructs binary <em>n</em>-leaf semi-directed level-1 networks in <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span> time from its quarnets (4-leaf subnetworks). Our method assumes we have direct access to all quarnets, yet uses only an asymptotically optimal number of <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>log</mi><mo>⁡</mo><mi>n</mi><mo>)</mo></math></span> quarnets. When the network is assumed to contain no triangles, our method instead relies only on four-cycle quarnets and the splits of the other quarnets. A variant of our algorithm works with quartets rather than quarnets and we show that it reconstructs most of a semi-directed level-1 network from an asymptotically optimal <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>log</mi><mo>⁡</mo><mi>n</mi><mo>)</mo></math></span> of the quartets it displays. Additionally, we provide an <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>)</mo></math></span> time algorithm that reconstructs the tree-of-blobs of any binary <em>n</em>-leaf semi-directed network with unbounded level from <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>)</mo></math></span> splits of its quarnets.</div></div>","PeriodicalId":50224,"journal":{"name":"Journal of Computer and System Sciences","volume":"152 ","pages":"Article 103655"},"PeriodicalIF":1.1,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143715791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Languages given by finite automata over the unary alphabet 有限自动机在一元字母表上给出的语言

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-08-01 Epub Date: 2025-02-05 DOI: 10.1016/j.jcss.2025.103634

Wojciech Czerwiński , Maciej Dębski , Tomasz Gogasz , Gordon Hoi , Sanjay Jain , Michał Skrzypczak , Frank Stephan , Christopher Tan

{"title":"Languages given by finite automata over the unary alphabet","authors":"Wojciech Czerwiński , Maciej Dębski , Tomasz Gogasz , Gordon Hoi , Sanjay Jain , Michał Skrzypczak , Frank Stephan , Christopher Tan","doi":"10.1016/j.jcss.2025.103634","DOIUrl":"10.1016/j.jcss.2025.103634","url":null,"abstract":"<div><div>This paper studies the complexity of operations on finite automata and the complexity of their decision problems when the alphabet is unary. Let <em>n</em> denote the number of states of the input automata considered. The following main results are obtained:</div><div>(1) Equality and inclusion of NFAs can be decided within time <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>O</mi><mo>(</mo><msup><mrow><mo>(</mo><mi>n</mi><mi>log</mi><mo>⁡</mo><mi>n</mi><mo>)</mo></mrow><mrow><mn>1</mn><mo>/</mo><mn>3</mn></mrow></msup><mo>)</mo></mrow></msup></math></span>. The previous upper bound <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>O</mi><mo>(</mo><msup><mrow><mo>(</mo><mi>n</mi><mi>log</mi><mo>⁡</mo><mi>n</mi><mo>)</mo></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><mo>)</mo></mrow></msup></math></span> was by Chrobak (1986).</div><div>(2) One can determine a UFA (unambiguous finite automata) for complement of another UFA or union of two UFAs using at most quasipolynomial number of states. However, for concatenation of two <em>n</em>-state UFAs, the worst case is a UFA having <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>Θ</mi><mo>(</mo><msup><mrow><mo>(</mo><mi>n</mi><msup><mrow><mi>log</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>⁡</mo><mi>n</mi><mo>)</mo></mrow><mrow><mn>1</mn><mo>/</mo><mn>3</mn></mrow></msup><mo>)</mo></mrow></msup></math></span> states.</div><div>(3) Results when an infinite <em>ω</em>-word given by a UFA or an NFA is a member of a given regular <em>ω</em>-language are obtained.</div></div>","PeriodicalId":50224,"journal":{"name":"Journal of Computer and System Sciences","volume":"151 ","pages":"Article 103634"},"PeriodicalIF":1.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143419429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Induced tree covering and the generalized Yutsis property 诱导树木覆盖和广义Yutsis性质

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-08-01 Epub Date: 2025-02-13 DOI: 10.1016/j.jcss.2025.103636

Luís Cunha , Gabriel Duarte , Fábio Protti , Loana Nogueira , Uéverton Souza

引用次数: 0

Destroying densest subgraphs is hard 破坏最密集的子图是困难的

IF 1.1 3区计算机科学

Journal of Computer and System Sciences Pub Date : 2025-08-01 Epub Date: 2025-02-13 DOI: 10.1016/j.jcss.2025.103635

Cristina Bazgan , André Nichterlein , Sofia Vazquez Alferez

{"title":"Destroying densest subgraphs is hard","authors":"Cristina Bazgan , André Nichterlein , Sofia Vazquez Alferez","doi":"10.1016/j.jcss.2025.103635","DOIUrl":"10.1016/j.jcss.2025.103635","url":null,"abstract":"<div><div>We analyze the computational complexity of the following computational problems called <span>Bounded-Density Edge Deletion</span> and <span>Bounded-Density Vertex Deletion</span>: Given a graph <em>G</em>, a budget <em>k</em> and a target density <span><math><msub><mrow><mi>τ</mi></mrow><mrow><mi>ρ</mi></mrow></msub></math></span>, are there <em>k</em> edges (<em>k</em> vertices) whose removal from <em>G</em> results in a graph where the densest subgraph has density at most <span><math><msub><mrow><mi>τ</mi></mrow><mrow><mi>ρ</mi></mrow></msub></math></span>? Here, the density of a graph is the number of its edges divided by the number of its vertices. We prove that both problems are polynomial-time solvable on trees and cliques but are NP-complete on planar bipartite graphs and split graphs. From a parameterized point of view, we show that both problems are fixed-parameter tractable with respect to the vertex cover number but W[1]-hard with respect to the solution size. Furthermore, we prove that <span>Bounded-Density Edge Deletion</span> is W[1]-hard with respect to the feedback edge number, demonstrating that the problem remains hard on very sparse graphs.</div></div>","PeriodicalId":50224,"journal":{"name":"Journal of Computer and System Sciences","volume":"151 ","pages":"Article 103635"},"PeriodicalIF":1.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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