Ildikó Schlotter

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In the k-Apex problem the task is to find at most k vertices whose deletion makes the given graph planar. The graphs for which there exists a solution form a minor closed class of graphs, hence by the deep results of Robertson and Seymour (J. Comb. Theory, Ser. B 63(1):65–110, 1995; J. Comb. Theory, Ser. B 92(2):325–357, 2004), there is a cubic algorithm(More)
We consider the computational complexity of a problem modeling bribery in the context of voting systems. In the scenario of Swap Bribery, each voter assigns a certain price for swapping the positions of two consecutive candidates in his preference ranking. The question is whether it is possible, without exceeding a given budget, to bribe the voters in a way(More)
As Bin Packing is NP-hard already for k = 2 bins, it is unlikely to be solvable in polynomial time even if the number of bins is a fixed constant. However, if the sizes of the items are polynomially bounded integers, then the problem can be solved in time n for an input of length n by dynamic programming. We show, by proving the W[1]-hardness of Unary Bin(More)
We study the Hospitals/Residents with Couples problem, a variant of the classical Stable Marriage problem. This is the extension of the Hospitals/Residents problem where residents are allowed to form pairs and submit joint rankings over hospitals. We use the framework of parameterized complexity, considering the number of couples as a parameter. We also(More)
We study a family of problems where the goal is to make a graph Eulerian, i.e., connected and with all the vertices having even degrees, by a minimum number of deletions. We completely classify the parameterized complexity of various versions: undirected or directed graphs, vertex or edge deletions, with or without the requirement of connectivity, etc. The(More)
We consider the variant of the classical Stable Marriage problem where preference lists can be incomplete and may contain ties. In such a setting, finding a stable matching of maximum size is NP-hard. We study the parameterized complexity of this problem, where the parameter can be the number of ties, the maximum or the overall length of ties. We also(More)
The model of a housing market, introduced by Shapley and Scarf in 1974 [14], captures a fundamental situation in an economy where each agent owns exactly one unit of some indivisible good: a house. We focus on an extension of this model where duplicate houses may exist. As opposed to the classical setting, the existence of an economical equilibrium is no(More)
We investigate a special case of the Induced Subgraph Isomorphism problem, where both input graphs are interval graphs. We show the NP-hardness of this problem, and we prove fixed-parameter tractability of the problem with non-standard parameterization, where the parameter is the difference |V(G)|−|V(H)|, with G and H being the larger and the smaller input(More)
In practical applications, algorithms for the classic version of the hospitals residents problem (the many-one version of the stable marriage problem) may have to be extended to accommodate the needs of couples who wish to be allocated to (geographically) compatible places. Such an extension has been in operation in the National Resident Matching Problem(More)
Approval-like voting rules, such as sincere-strategy preference-based approval voting (SP-AV), the Bucklin rule (an adaptive variant of k-approval voting), and the Fallback rule (a hybrid of the Bucklin rule and SP-AV) have many desirable properties: for example, they are easy to understand and encourage the candidates to choose electoral platforms that(More)