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Generalised hypertree width ($ghw$) is a hypergraph parameter that is central to the tractability of many prominent problems with natural hypergraph structure. Computing $ghw$ of a hypergraph is notoriously hard. The decision version of the…

Data Structures and Algorithms · Computer Science 2024-01-09 Matthias Lanzinger , Igor Razgon

Phylogenetic networks provide a way to describe and visualize evolutionary histories that have undergone so-called reticulate evolutionary events such as recombination, hybridization or horizontal gene transfer. The level k of a network…

Populations and Evolution · Quantitative Biology 2008-07-21 Leo van Iersel , Steven Kelk , Matthias Mnich

We consider the well-studied problem of finding a spanning tree with minimum average distance between vertex pairs (called a MAD tree). This is a classic network design problem which is known to be NP-hard. While approximation algorithms…

Data Structures and Algorithms · Computer Science 2026-04-01 Tom-Lukas Breitkopf , Vincent Froese , Anton Herrmann , André Nichterlein , Camille Richer

The maximum common subtree isomorphism problem asks for the largest possible isomorphism between subtrees of two given input trees. This problem is a natural restriction of the maximum common subgraph problem, which is ${\sf NP}$-hard in…

Data Structures and Algorithms · Computer Science 2016-08-23 Andre Droschinsky , Nils M. Kriege , Petra Mutzel

Phylogenetic networks are directed acyclic graphs that depict the genomic evolution of related taxa. Reticulation nodes in such networks (nodes with more than one parent) represent reticulate evolutionary events, such as recombination,…

Populations and Evolution · Quantitative Biology 2024-11-21 Alexey Markin , Sriram Vijendran , Oliver Eulenstein

Phylogenetic trees canonically arise as embeddings of phylogenetic networks. We recently showed that the problem of deciding if two phylogenetic networks embed the same sets of phylogenetic trees is computationally hard, \blue{in…

Combinatorics · Mathematics 2021-04-13 Janosch Doecker , Simone Linz , Charles Semple

A graph G is called well-indumatched if all of its maximal induced matchings have the same size. In this paper we characterize all well-indumatched trees. We provide a linear time algorithm to decide if a tree is well-indumatched or not.…

Discrete Mathematics · Computer Science 2019-12-18 S. Akbari , T. Ekim , A. H. Ghodrati , S. Zare

The hybridization number problem requires us to embed a set of binary rooted phylogenetic trees into a binary rooted phylogenetic network such that the number of nodes with indegree two is minimized. However, from a biological point of view…

Data Structures and Algorithms · Computer Science 2016-09-05 Leo van Iersel , Steven Kelk , Georgios Stamoulis , Leen Stougie , Olivier Boes

A resolving set $S$ of a graph $G$ is a subset of its vertices such that no two vertices of $G$ have the same distance vector to $S$. The Metric Dimension problem asks for a resolving set of minimum size, and in its decision form, a…

Computational Complexity · Computer Science 2019-07-19 Édouard Bonnet , Nidhi Purohit

Consider a set of labels $L$ and a set of trees ${\mathcal T} = \{{\mathcal T}^{(1), {\mathcal T}^{(2), ..., {\mathcal T}^{(k) \$ where each tree ${\mathcal T}^{(i)$ is distinctly leaf-labeled by some subset of $L$. One fundamental problem…

Data Structures and Algorithms · Computer Science 2008-02-21 Viet Tung Hoang , Wing-Kin Sung

We present the first fixed-parameter tractable (FPT) algorithms for exact computation of generalized hypertree width (ghw) and fractional hypertree width (fhw). Our algorithms are parameterized by the target width, the rank, and the maximum…

Data Structures and Algorithms · Computer Science 2026-03-16 Matthias Lanzinger , Igor Razgon , Daniel Unterberger

Phylogenetic trees illustrate the evolutionary history of genes and species. In most cases, although genes evolve along with the species they belong to, a species tree and gene tree are not identical, because of evolutionary events at the…

Data Structures and Algorithms · Computer Science 2019-02-25 Damir Hasic , Eric Tannier

An evolutionary tree (phylogenetic tree) is a binary, rooted, unordered tree that models the evolutionary history of currently living species in which leaves are labeled by species. In this paper, we investigate the problem of finding the…

Populations and Evolution · Quantitative Biology 2013-04-02 Soheil Jahangiri Tazehkand , Seyed Naser Hashemi , Hadi Poormohammadi

Phylogenetic trees and networks are leaf-labelled graphs that are used to describe evolutionary histories of species. The Tree Containment problem asks whether a given phylogenetic tree is embedded in a given phylogenetic network. Given a…

Populations and Evolution · Quantitative Biology 2010-06-17 Leo van Iersel , Charles Semple , Mike Steel

There are many classical problems in P whose time complexities have not been improved over the past decades. Recent studies of "Hardness in P" have revealed that, for several of such problems, the current fastest algorithm is the best…

Data Structures and Algorithms · Computer Science 2017-10-24 Yoichi Iwata , Tomoaki Ogasawara , Naoto Ohsaka

Comparative analyses of phylogenetic trees typically require identical taxon sets, however, in practice, trees often include distinct but overlapping taxa. Pruning non-shared leaves discards phylogenetic signal, whereas tree completion can…

Populations and Evolution · Quantitative Biology 2026-04-28 Aleksandr Koshkarov , Nadia Tahiri

For a phylogenetic tree, the phylogenetic diversity of a set A of taxa is the total weight of edges on paths to A. Finding small sets of maximal diversity is crucial for conservation planning, as it indicates where limited resources can be…

Data Structures and Algorithms · Computer Science 2025-10-29 Mark Jones , Jannik Schestag

A classical problem in phylogenetic tree analysis is to decide whether there is a phylogenetic tree $T$ that contains all information of a given collection $\cP$ of phylogenetic trees. If the answer is "yes" we say that $\cP$ is compatible…

Combinatorics · Mathematics 2010-06-29 Stefan Grünewald

Given a rooted, binary phylogenetic network and a rooted, binary phylogenetic tree, can the tree be embedded into the network? This problem, called \textsc{Tree Containment}, arises when validating networks constructed by phylogenetic…

Populations and Evolution · Quantitative Biology 2024-02-14 Leo van Iersel , Mark Jones , Mathias Weller

In the NP-hard Optimizing PD with Dependencies (PDD) problem, the input consists of a phylogenetic tree $T$ over a set of taxa $X$, a food-web that describes the prey-predator relationships in $X$, and integers $k$ and $D$. The task is to…

Computational Complexity · Computer Science 2024-05-28 Christian Komusiewicz , Jannik Schestag