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We investigate a process of joining $k$ random spanning trees on a fixed clique $K_n$. The joined trees may not be disjoint and multiple edges are replaced by one simple edge. This process produces a simple graph $G$ on $n$~vertices with an…

Discrete Mathematics · Computer Science 2025-11-25 Blazej Wrobel , Dominik Bojko

We provide the first algorithm for computing an optimal tree decomposition for a given graph $G$ that runs in single exponential time in the feedback vertex number of $G$, that is, in time $2^{O(\text{fvn}(G))}\cdot n^{O(1)}$, where…

Data Structures and Algorithms · Computer Science 2026-05-19 Hendrik Molter , Meirav Zehavi , Amit Zivan

The {\sc Directed Maximum Leaf Out-Branching} problem is to find an out-branching (i.e. a rooted oriented spanning tree) in a given digraph with the maximum number of leaves. In this paper, we obtain two combinatorial results on the number…

Data Structures and Algorithms · Computer Science 2008-03-06 N Alon , F. V. Fomin , G. Gutin , M. Krivelevich , S. Saurabh

Let $k\geq2$ be an integer. A tree $T$ is called a $k$-tree if $d_T(v)\leq k$ for each $v\in V(T)$, that is, the maximum degree of a $k$-tree is at most $k$. Let $\lambda_1(D(G))$ denote the distance spectral radius in $G$, where $D(G)$…

Combinatorics · Mathematics 2024-07-22 Sizhong Zhou , Jiancheng Wu

For a fixed integer $k\ge 2$, a $k$-community structure in an undirected graph is a partition of its vertex set into $k$ sets called communities, each of size at least two, such that every vertex of the graph has proportionally at least as…

Combinatorics · Mathematics 2023-12-08 Narmina Baghirova , Clément Dallard , Bernard Ries , David Schindl

Let $G$ be a connected graph and $T$ a spanning tree of $G$. Let $\rho(G)$ denote the adjacency spectral radius of $G$. The $k$-excess of a vertex $v$ in $T$ is defined as $\max\{0,d_T(v)-k\}$. The total $k$-excess $\mbox{te}(T,k)$ is…

Combinatorics · Mathematics 2026-03-24 Sizhong Zhou

We study the problem of finding small trees. Classical network design problems are considered with the additional constraint that only a specified number $k$ of nodes are required to be connected in the solution. A prototypical example is…

Combinatorics · Mathematics 2009-09-25 R. Ravi , R. Sundaram , Madhav V. Marathe , S. S. Ravi , Daniel J. Rosenkrantz

Consider the following generalization of the classic binary search problem: a searcher is required to find a hidden vertex $x$ in a tree $T$. To do so, they iteratively perform queries to an oracle, each about a chosen vertex $v$. After…

Data Structures and Algorithms · Computer Science 2025-10-01 Michał Szyfelbein

Computing bounded depth decompositions is a bottleneck in many applications of the treedepth parameter. The fastest known algorithm, which is due to Reidl, Rossmanith, S\'{a}nchez Villaamil, and Sikdar [ICALP 2014], runs in…

Data Structures and Algorithms · Computer Science 2025-02-25 Lars Jaffke , Paloma T. de Lima , Wojciech Nadara , Emmanuel Sam

Motivated by an application from geodesy, we introduce a novel clustering problem which is a $k$-center (or k-diameter) problem with a side constraint. For the side constraint, we are given an undirected connectivity graph $G$ on the input…

Data Structures and Algorithms · Computer Science 2023-10-19 Lukas Drexler , Jan Eube , Kelin Luo , Dorian Reineccius , Heiko Röglin , Melanie Schmidt , Julian Wargalla

We consider the problem of learning the structure of undirected graphical models with bounded treewidth, within the maximum likelihood framework. This is an NP-hard problem and most approaches consider local search techniques. In this…

Machine Learning · Computer Science 2012-12-12 K. S. Sesh Kumar , Francis Bach

We consider the problem of computing a Steiner tree of minimum cost under a hop constraint which requires the depth of the tree to be at most $k$. Our main result is an exact algorithm for metrics induced by graphs with bounded treewidth…

Data Structures and Algorithms · Computer Science 2022-10-12 Martin Böhm , Ruben Hoeksma , Nicole Megow , Lukas Nölke , Bertrand Simon

Tree-decompositions and treewidth are of fundamental importance in structural and algorithmic graph theory. The "spread" of a tree-decomposition is the minimum integer $s$ such that every vertex lies in at most $s$ bags. A…

Combinatorics · Mathematics 2026-04-08 Marc Distel , Neel Kaul , Raj Kaul , David R. Wood

Given a reference set $R$ of $n$ points and a query set $Q$ of $m$ points in a metric space, this paper studies an important problem of finding $k$-nearest neighbors of every point $q \in Q$ in the set $R$ in a near-linear time. In the…

Computational Geometry · Computer Science 2024-03-05 Yury Elkin , Vitaliy Kurlin

k-means is a widely used clustering algorithm, but for $k$ clusters and a dataset size of $N$, each iteration of Lloyd's algorithm costs $O(kN)$ time. Although there are existing techniques to accelerate single Lloyd iterations, none of…

Data Structures and Algorithms · Computer Science 2016-01-18 Ryan R. Curtin

In collective tree exploration, a team of $k$ mobile agents is tasked to go through all edges of an unknown tree as fast as possible. An edge of the tree is revealed to the team when one agent becomes adjacent to that edge. The agents start…

Data Structures and Algorithms · Computer Science 2023-11-01 Romain Cosson

In this paper, we study some spanning trees with bounded degree and leaf degree from eigenvalues. For any integer $k\geq2$, a $k$-tree is a spanning tree in which every vertex has degree no more than $k$. Let $T$ be a spanning tree of a…

Combinatorics · Mathematics 2024-07-29 Chang Liu , Jianping Li

Given an edge-weighted graph, how many minimum $k$-cuts can it have? This is a fundamental question in the intersection of algorithms, extremal combinatorics, and graph theory. It is particularly interesting in that the best known bounds…

Data Structures and Algorithms · Computer Science 2019-06-04 Anupam Gupta , Euiwoong Lee , Jason Li

The Rooted Maximum Leaf Outbranching problem consists in finding a spanning directed tree rooted at some prescribed vertex of a digraph with the maximum number of leaves. Its parameterized version asks if there exists such a tree with at…

Discrete Mathematics · Computer Science 2009-04-20 Jean Daligault , Stephan Thomasse

We consider the ``minimum degree spanning tree'' problem. As input, we receive an undirected, connected graph $G=(V, E)$ with $n$ nodes and $m$ edges, and our task is to find a spanning tree $T$ of $G$ that minimizes $\max_{u \in V}…

Data Structures and Algorithms · Computer Science 2026-03-02 Sayan Bhattacharya , Ermiya Farokhnejad , Haoze Wang