All Outputs (19)

Computing subset transversals in H-free graphs (2021)
Journal Article
Brettell, N., Johnson, M., Paesani, G., & Paulusma, D. (2022). Computing subset transversals in H-free graphs. Theoretical Computer Science, 902, 76-92. https://doi.org/10.1016/j.tcs.2021.12.010

we study the computational complexity of two well-known graph transversal problems, namely Subset Feedback Vertex Set and Subset Odd Cycle Transversal, by restricting the input to H-free graphs, that is, to graphs that do not contain some fixed graph... Read More about Computing subset transversals in H-free graphs.

Tree pivot-minors and linear rank-width (2021)
Journal Article
Dabrowski, K., Dross, F., Jeong, J., Kante, M., Kwon, O., Oum, S., & Paulusma, D. (2021). Tree pivot-minors and linear rank-width. SIAM Journal on Discrete Mathematics, 35(4), 2922-2945. https://doi.org/10.1137/21m1402339

Tree-width and its linear variant path-width play a central role for the graph minor relation. In particular, Robertson and Seymour (1983) proved that for every tree T, the class of graphs that do not contain T as a minor has bounded path-width. For... Read More about Tree pivot-minors and linear rank-width.

Partitioning H-free graphs of bounded diameter (2021)
Conference Proceeding
Brause, C., Golovach, P. A., Martin, B., Paulusma, D., & Smith, S. (2021). Partitioning H-free graphs of bounded diameter. In H. Ahn, & K. Sadakane (Eds.), . https://doi.org/10.4230/lipics.isaac.2021.21

A natural way of increasing our understanding of NP-complete graph problems is to restrict the input to a special graph class. Classes of H-free graphs, that is, graphs that do not contain some graph H as an induced subgraph, have proven to be an ide... Read More about Partitioning H-free graphs of bounded diameter.

Induced disjoint paths in AT-free graphs (2021)
Journal Article
Golovach, P., Paulusma, D., & van Leeuwen, E. (2022). Induced disjoint paths in AT-free graphs. Journal of Computer and System Sciences, 124, 170-191. https://doi.org/10.1016/j.jcss.2021.10.003

Paths P1, . . . , Pk in a graph G = (V, E) are mutually induced if any two distinct Pi and Pj have neither common vertices nor adjacent vertices (except perhaps their end-vertices). The Induced Disjoint Paths problem is to decide if a graph G with k... Read More about Induced disjoint paths in AT-free graphs.

Disjoint paths and connected subgraphs for H-free graphs (2021)
Journal Article
Kern, W., Martin, B., Paulusma, D., Smith, S., & van Leeuwen, E. (2022). Disjoint paths and connected subgraphs for H-free graphs. Theoretical Computer Science, 898, 59-68. https://doi.org/10.1016/j.tcs.2021.10.019

The well-known Disjoint Paths problem is to decide if a graph contains k pairwise disjoint paths, each connecting a different terminal pair from a set of k distinct vertex pairs. We determine, with an exception of two cases, the complexity of the Dis... Read More about Disjoint paths and connected subgraphs for H-free graphs.

Hard problems that quickly become very easy (2021)
Journal Article
Martin, B., Paulusma, D., & Smith, S. (2022). Hard problems that quickly become very easy. Information Processing Letters, 174, https://doi.org/10.1016/j.ipl.2021.106213

A graph class is hereditary if it is closed under vertex deletion. We give examples of NP-hard, PSPACE-complete and NEXPTIME-complete problems that become constant-time solvable for every hereditary graph class that is not equal to the class of all g... Read More about Hard problems that quickly become very easy.

Acyclic, star and injective colouring: bounding the diameter (2021)
Conference Proceeding
Brause, C., Golovach, P., Martin, B., Paulusma, D., & Smith, S. (2021). Acyclic, star and injective colouring: bounding the diameter. In Ł. Kowalik, M. Pilipczuk, & P. Rzążewski (Eds.), Graph-Theoretic Concepts in Computer Science: 47th International Workshop, WG 2021, Warsaw, Poland, June 23–25, 2021, Revised Selected Papers (336-348). https://doi.org/10.1007/978-3-030-86838-3_26

We examine the effect of bounding the diameter for wellstudied variants of the Colouring problem. A colouring is acyclic, star, or injective if any two colour classes induce a forest, star forest or disjoint union of vertices and edges, respectively.... Read More about Acyclic, star and injective colouring: bounding the diameter.

QCSP on reflexive tournaments (2021)
Conference Proceeding
Larose, B., Markovic, P., Martin, B., Paulusma, D., Smith, S., & Zivny, S. (2021). QCSP on reflexive tournaments. In P. Mutzel, R. Pagh, & G. Herman (Eds.), . https://doi.org/10.4230/lipics.esa.2021.58

We give a complexity dichotomy for the Quantified Constraint Satisfaction Problem QCSP(H) when H is a reflexive tournament. It is well-known that reflexive tournaments can be split into a sequence of strongly connected components H1, . . . , Hn so th... Read More about QCSP on reflexive tournaments.

Bounding the mim-width of hereditary graph classes (2021)
Journal Article
Brettell, N., Horsfield, J., Munaro, A., Paesani, G., & Paulusma, D. (2022). Bounding the mim-width of hereditary graph classes. Journal of Graph Theory, 99(1), 117-151. https://doi.org/10.1002/jgt.22730

A large number of NP-hard graph problems are solvable in XP time when parameterized by some width parameter. Hence, when solving problems on special graph classes, it is helpful to know if the graph class under consideration has bounded width. In thi... Read More about Bounding the mim-width of hereditary graph classes.

Feedback Vertex Set and Even Cycle Transversal for H-free graphs: finding large block graphs (2021)
Conference Proceeding
Paesani, G., Paulusma, D., & Rzążewski, P. (2021). Feedback Vertex Set and Even Cycle Transversal for H-free graphs: finding large block graphs. In F. Bonchi, & S. J. Puglisi (Eds.), . https://doi.org/10.4230/lipics.mfcs.2021.82

We prove new complexity results for Feedback Vertex Set and Even Cycle Transversal on H-free graphs, that is, graphs that do not contain some fixed graph H as an induced subgraph. In particular, we prove that both problems are polynomial-time solvabl... Read More about Feedback Vertex Set and Even Cycle Transversal for H-free graphs: finding large block graphs.

Computing weighted subset transversals in H-free graphs (2021)
Conference Proceeding
Brettell, N., Johnson, M., & Paulusma, D. (2021). Computing weighted subset transversals in H-free graphs. In A. Lubiw, M. Salavatipour, & M. He (Eds.), Algorithms and Data Structures 17th International Symposium, WADS 2021, Virtual Event, August 9–11, 2021, Proceedings (229-242). https://doi.org/10.1007/978-3-030-83508-8_17

For the Odd Cycle Transversal problem, the task is to nd a small set S of vertices in a graph that intersects every cycle of odd length. The Subset Odd Cycle Transversal requires S to intersect only those odd cycles that include a vertex of a disting... Read More about Computing weighted subset transversals in H-free graphs.

Solving problems on generalized convex graphs via mim-width (2021)
Conference Proceeding
Bonomo-Braberman, F., Brettell, N., Munaro, A., & Paulusma, D. (2021). Solving problems on generalized convex graphs via mim-width. In A. Lubiw, M. Salavatipour, & M. He (Eds.), Algorithms and Data Structures: 17th International Symposium, WADS 2021, Virtual Event, August 9–11, 2021, Proceedings (200-214). https://doi.org/10.1007/978-3-030-83508-8_15

A bipartite graph G = (A, B, E) is H-convex, for some family of graphs H, if there exists a graph H ∈ H with V (H) = A such that the set of neighbours in A of each b ∈ B induces a connected subgraph of H. Many NP-complete problems become polynomial-t... Read More about Solving problems on generalized convex graphs via mim-width.

List k-colouring P-free graphs: a mim-width perspective (2021)
Journal Article
Brettell, N., Horsfield, J., Munaro, A., & Paulusma, D. (2022). List k-colouring P-free graphs: a mim-width perspective. Information Processing Letters, 173, Article 106168. https://doi.org/10.1016/j.ipl.2021.106168

A colouring of a graph G = (V, E) is a mapping c : V → {1, 2, . . .} such that c(u) 6= c(v) for every two adjacent vertices u and v of G. The List k-Colouring problem is to decide whether a graph G = (V, E) with a list L(u) ⊆ {1, . . . , k} for each... Read More about List k-colouring P-free graphs: a mim-width perspective.

Disjoint paths and connected subgraphs for H-free graphs (2021)
Conference Proceeding
Kern, W., Martin, B., Paulusma, D., Smith, S., & van Leeuwen, E. (2021). Disjoint paths and connected subgraphs for H-free graphs. In P. Flocchini, & L. Moura (Eds.), Combinatorial Algorithms: 32nd International Workshop, IWOCA 2021, Ottawa, ON, Canada, July 5–7, 2021, Proceedings (414-427). https://doi.org/10.1007/978-3-030-79987-8_29

The well-known Disjoint Paths problem is to decide if a graph contains k pairwise disjoint paths, each connecting a different terminal pair from a set of k distinct pairs. We determine, with an exception of two cases, the complexity of the Disjoint P... Read More about Disjoint paths and connected subgraphs for H-free graphs.

Injective colouring for H-free graphs (2021)
Conference Proceeding
Bok, J., Jedličková, N., Martin, B., Paulusma, D., & Smith, S. (2021). Injective colouring for H-free graphs.

A function c : V (G) → {1, 2, . . . , k} is a k-colouring of a graph G if c(u) 6= c(v) whenever u and v are adjacent. If any two colour classes induce the disjoint union of vertices and edges, then c is called injective. Injective colourings are also... Read More about Injective colouring for H-free graphs.

Recognizing Graphs Close to Bipartite Graphs with an Application to Colouring Reconfiguration (2021)
Journal Article
Bonamy, M., Dabrowski, K., Feghali, C., Johnson, M., & Paulusma, D. (2021). Recognizing Graphs Close to Bipartite Graphs with an Application to Colouring Reconfiguration. Journal of Graph Theory, 98(1), 81-109. https://doi.org/10.1002/jgt.22683

We continue research into a well-studied family of problems that ask whether the vertices of a given graph can be partitioned into sets A and B, where A is an independent set and B induces a graph from some specified graph class G. We consider the ca... Read More about Recognizing Graphs Close to Bipartite Graphs with an Application to Colouring Reconfiguration.

Colouring graphs of bounded diameter in the absence of small cycles (2021)
Conference Proceeding
Martin, B., Paulusma, D., & Smith, S. (2021). Colouring graphs of bounded diameter in the absence of small cycles. In T. Calamoneri, & F. Corò (Eds.), . https://doi.org/10.1007/978-3-030-75242-2_26

For k ≥ 1, a k-colouring c of G is a mapping from V (G) to {1, 2, . . . , k} such that c(u) 6= c(v) for any two non-adjacent vertices u and v. The k-Colouring problem is to decide if a graph G has a k-colouring. For a family of graphs H, a graph G is... Read More about Colouring graphs of bounded diameter in the absence of small cycles.

What graphs are 2-dot product graphs? (2021)
Journal Article
Johnson, M., Paulusma, D., & van Leeuwen, E. (2021). What graphs are 2-dot product graphs?. International Journal of Computational Geometry and Applications, 31(01), 1-16. https://doi.org/10.1142/s0218195921500011

Let d ≥ 1 be an integer. From a set of d-dimensional vectors, we obtain a d-dot product graph by letting each vector a u correspond to a vertex u and by adding an edge between two vertices u and v if and only if their dot product a u · a v ≥ t, for s... Read More about What graphs are 2-dot product graphs?.

Steiner Trees for Hereditary Graph Classes: a Treewidth Perspective (2021)
Journal Article
Bodlaender, H., Brettell, N., Johnson, M., Paesani, G., Paulusma, D., & van Leeuwen, E. (2021). Steiner Trees for Hereditary Graph Classes: a Treewidth Perspective. Theoretical Computer Science, 867, 30-39. https://doi.org/10.1016/j.tcs.2021.03.012

We consider the classical problems (Edge) Steiner Tree and Vertex Steiner Tree after restricting the input to some class of graphs characterized by a small set of forbidden induced subgraphs. We show a dichotomy for the former problem restricted to -... Read More about Steiner Trees for Hereditary Graph Classes: a Treewidth Perspective.