Professor Daniel Paulusma's Outputs (311)

Surjective H-Colouring over Reflexive Digraphs (2018)
Presentation / Conference Contribution
Larose, B., Martin, B., & Paulusma, D. (2023, February). Surjective H-Colouring over Reflexive Digraphs. Presented at 35th Symposium on Theoretical Aspects of Computer Science (STACS 2018), Caen, France

The Surjective H-Colouring problem is to test if a given graph allows a vertex-surjective homomorphism to a fixed graph H. The complexity of this problem has been well studied for undirected (partially) reflexive graphs. We introduce endo-triviality,... Read More about Surjective H-Colouring over Reflexive Digraphs.

On the price of independence for vertex cover, feedback vertex set and odd cycle transversal (2018)
Presentation / Conference Contribution
Dabrowski, K. K., Johnson, M., Paesani, G., Paulusma, D., & Zamaraev, V. (2018, August). On the price of independence for vertex cover, feedback vertex set and odd cycle transversal. Presented at 43nd International Symposium on Mathematical Foundations of Computer Science (MFCS 2018)., Liverpool, UK

Let vc(G), fvs(G) and oct(G) denote, respectively, the size of a minimum vertex cover, minimum feedback vertex set and minimum odd cycle transversal in a graph G. One can ask, when looking for these sets in a graph, how much bigger might they be if w... Read More about On the price of independence for vertex cover, feedback vertex set and odd cycle transversal.

Disconnected Cuts in Claw-free Graphs (2018)
Presentation / Conference Contribution
Martin, B., Paulusma, D., & van Leeuwen, E. J. (2018, August). Disconnected Cuts in Claw-free Graphs. Presented at 26th Annual European Symposium on Algorithms (ESA 2018)., Helsinki, Finland

A disconnected cut of a connected graph is a vertex cut that itself also induces a disconnected subgraph. The corresponding decision problem is called Disconnected Cut. It is known that Disconnected Cut is NP-hard on general graphs, while polynomial-... Read More about Disconnected Cuts in Claw-free Graphs.

Clique-Width for Graph Classes Closed under Complementation (2017)
Presentation / Conference Contribution
Blanché, A., Dabrowski, K. K., Johnson, M., Lozin, V. V., Paulusma, D., & Zamaraev, V. (2017, August). Clique-Width for Graph Classes Closed under Complementation. Presented at 42nd International Symposium on Mathematical Foundations of Computer Science (MFCS)., Aalborg, Denmark

Clique-width is an important graph parameter due to its algorithmic and structural properties. A graph class is hereditary if it can be characterized by a (not necessarily finite) set H of forbidden induced subgraphs. We initiate a systematic study i... Read More about Clique-Width for Graph Classes Closed under Complementation.

Finding cactus roots in polynomial time (2017)
Journal Article
Golovach, P., Kratsch, D., Stewart, A., & Paulusma, D. (2018). Finding cactus roots in polynomial time. Theory of Computing Systems, 62(6), 1409-1426. https://doi.org/10.1007/s00224-017-9825-2

A graph H is a square root of a graph G, or equivalently, G is the square of H, if G can be obtained from H by adding an edge between any two vertices in H that are of distance 2. The SQUARE ROOT problem is that of deciding whether a given graph admi... Read More about Finding cactus roots in polynomial time.

Independent feedback vertex sets for graphs of bounded diameter (2017)
Journal Article
Bonamy, M., Dabrowski, K., Feghali, C., Johnson, M., & Paulusma, D. (2018). Independent feedback vertex sets for graphs of bounded diameter. Information Processing Letters, 131, 26-32. https://doi.org/10.1016/j.ipl.2017.11.004

The Near-Bipartiteness problem is that of deciding whether or not the vertices of a graph can be partitioned into sets A and B, where A is an independent set and B induces a forest. The set A in such a partition is said to be an independent feedback... Read More about Independent feedback vertex sets for graphs of bounded diameter.

Clique-width and well-quasi ordering of triangle-free graph classes (2017)
Presentation / Conference Contribution
Dabrowski, K. K., Lozin, V. V., & Paulusma, D. (2017, June). Clique-width and well-quasi ordering of triangle-free graph classes. Presented at WG 2017: 43rd International Workshop on Graph-Theoretic Concepts in Computer Science, Eindhoven, The Netherlands

Daligault, Rao and Thomassé asked whether every hereditary graph class that is well-quasi-ordered by the induced subgraph relation has bounded clique-width. Lozin, Razgon and Zamaraev (WG 2015) gave a negative answer to this question, but their count... Read More about Clique-width and well-quasi ordering of triangle-free graph classes.

Reducing the chromatic number by vertex or edge deletions (2017)
Presentation / Conference Contribution
Picouleau, C., Paulusma, D., & Ries, B. Reducing the chromatic number by vertex or edge deletions. Presented at LAGOS 2017: The IX Latin and American Algorithms, Graphs and Optimization Symposium., Marseille, France

A vertex or an edge in a graph is critical if its deletion reduces the chromatic number of the graph by one. We consider the problems of testing whether a graph has a critical vertex or a critical edge, respectively. We give a complete classification... Read More about Reducing the chromatic number by vertex or edge deletions.

Minimum connected transversals in graphs: New hardness results and tractable cases using the price of connectivity (2017)
Journal Article
Chiarelli, N., Hartinger, T., Johnson, M., Milanič, M., & Paulusma, D. (2018). Minimum connected transversals in graphs: New hardness results and tractable cases using the price of connectivity. Theoretical Computer Science, 705, 75-83. https://doi.org/10.1016/j.tcs.2017.09.033

We perform a systematic study in the computational complexity of the connected variant of three related transversal problems: Vertex Cover, Feedback Vertex Set, and Odd Cycle Transversal. Just like their original counterparts, these variants are NP-c... Read More about Minimum connected transversals in graphs: New hardness results and tractable cases using the price of connectivity.

Contracting bipartite graphs to paths and cycles (2017)
Presentation / Conference Contribution
Dabrowski, K., & Paulusma, D. Contracting bipartite graphs to paths and cycles. Presented at Eurocomb 2017: European Conference on Combinatorics, Graph Theory and Applications., Vienna, Austria

Testing if a given graph G contains the k-vertex path Pk as a minor or as an induced minor is trivial for every fixed integer k≥1. The situation changes for the problem of checking if a graph can be modified into Pk by using only edge contractions. I... Read More about Contracting bipartite graphs to paths and cycles.

Contracting Bipartite Graphs to Paths and Cycles (2017)
Journal Article
Dabrowski, K., & Paulusma, D. (2017). Contracting Bipartite Graphs to Paths and Cycles. Information Processing Letters, 127, 37-42. https://doi.org/10.1016/j.ipl.2017.06.013

Testing if a given graph G contains the k -vertex path Pk as a minor or as an induced minor is trivial for every fixed integer k≥1. However, the situation changes for the problem of checking if a graph can be modified into Pk by using only edge contr... Read More about Contracting Bipartite Graphs to Paths and Cycles.

Well-quasi-ordering versus clique-width: new results on bigenic classes (2017)
Journal Article
Dabrowski, K., Lozin, V., & Paulusma, D. (2018). Well-quasi-ordering versus clique-width: new results on bigenic classes. Order, 35(2), 253-274. https://doi.org/10.1007/s11083-017-9430-7

Daligault, Rao and Thomassé asked whether a hereditary class of graphs well-quasi-ordered by the induced subgraph relation has bounded clique-width. Lozin, Razgon and Zamaraev recently showed that this is not true for classes defined by infinitely ma... Read More about Well-quasi-ordering versus clique-width: new results on bigenic classes.

Algorithms for outerplanar graph roots and graph roots of pathwidth at most 2 (2017)
Presentation / Conference Contribution
Golovach, P., Heggernes, P., Kratsch, D., Lima, P., & Paulusma, D. (2017, June). Algorithms for outerplanar graph roots and graph roots of pathwidth at most 2. Presented at 43rd International Workshop on Graph-Theoretic Concepts in Computer Science (WG 2017), Eindhoven, The Netherlands

Deciding whether a given graph has a square root is a classical problem that has been studied extensively both from graph theoretic and from algorithmic perspectives. The problem is NP-complete in general, and consequently substantial effort has been... Read More about Algorithms for outerplanar graph roots and graph roots of pathwidth at most 2.

Colouring Diamond-free Graphs (2017)
Journal Article
Dabrowski, K., Dross, F., & Paulusma, D. (2017). Colouring Diamond-free Graphs. Journal of Computer and System Sciences, 89, 410-431. https://doi.org/10.1016/j.jcss.2017.06.005

The Colouring problem is that of deciding, given a graph G and an integer k, whether G admits a (proper) k-colouring. For all graphs H up to five vertices, we classify the computational complexity of Colouring for (diamond,H)-free graphs. Our proof i... Read More about Colouring Diamond-free Graphs.

Recognizing Graphs Close to Bipartite Graphs (2017)
Presentation / Conference Contribution
Bonamy, M., Dabrowski, K. K., Feghali, C., Johnson, M., & Paulusma, D. (2017, August). Recognizing Graphs Close to Bipartite Graphs. Presented at 42nd International Symposium on Mathematical Foundations of Computer Science (MFCS)., Aalborg, Denmark

We continue research into a well-studied family of problems that ask if the vertices of a 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 let G be the class of k-de... Read More about Recognizing Graphs Close to Bipartite Graphs.

A linear kernel for finding square roots of almost planar graphs (2017)
Journal Article
Golovach, P., Kratsch, D., Paulusma, D., & Stewart, A. (2017). A linear kernel for finding square roots of almost planar graphs. Theoretical Computer Science, 689, 36-47. https://doi.org/10.1016/j.tcs.2017.05.008

A graph H is a square root of a graph G if G can be obtained from H by the addition of edges between any two vertices in H that are at distance 2 from each other. The Square Root problem is that of deciding whether a given graph admits a square root.... Read More about A linear kernel for finding square roots of almost planar graphs.

Computing square roots of graphs with low maximum degree (2017)
Journal Article
Cochefert, M., Couturier, J., Golovach, P., Kratsch, D., Paulusma, D., & Stewart, A. (2018). Computing square roots of graphs with low maximum degree. Discrete Applied Mathematics, 248, 93-101. https://doi.org/10.1016/j.dam.2017.04.041

A graph H is a square root of a graph G if G can be obtained from H by adding an edge between any two vertices in H that are of distance 2. The Square Root problem is that of deciding whether a given graph admits a square root. This problem is known... Read More about Computing square roots of graphs with low maximum degree.

Surjective H-Colouring: new hardness results (2017)
Presentation / Conference Contribution
Golovach, P. A., Johnson, M., Martin, M., Paulusma, D., & Stewart, A. (2017, June). Surjective H-Colouring: new hardness results. Presented at Computability in Europe (CiE 2017)., Turku, Finland

A homomorphism from a graph G to a graph H is a vertex mapping f from the vertex set of G to the vertex set of H such that there is an edge between vertices f(u) and f(v) of H whenever there is an edge between vertices u and v of G. The H-Colouring p... Read More about Surjective H-Colouring: new hardness results.

Blocking independent sets for H-free graphs via edge contractions and vertex deletions (2017)
Presentation / Conference Contribution
Paulusma, D., Picouleau, C., & Ries, B. (2017, April). Blocking independent sets for H-free graphs via edge contractions and vertex deletions. Presented at Theory and applications of models of computation, 14th Annual Conference, TAMC 2017, Bern, Switzerland

Let d and k be two given integers, and let G be a graph. Can we reduce the independence number of G by at least d via at most k graph operations from some fixed set S? This problem belongs to a class of so-called blocker problems. It is known to be c... Read More about Blocking independent sets for H-free graphs via edge contractions and vertex deletions.

The Stable Fixtures Problem with Payments (2017)
Journal Article
Biró, P., Kern, W., Paulusma, D., & Wojuteczky, P. (2018). The Stable Fixtures Problem with Payments. Games and Economic Behavior, 108, 245-268. https://doi.org/10.1016/j.geb.2017.02.002

We consider multiple partners matching games (G,b,w), where G is a graph with an integer vertex capacity function b and an edge weighting w. If G is bipartite, these games are called multiple partners assignment games. We give a polynomial-time algor... Read More about The Stable Fixtures Problem with Payments.