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Algorithmic aspects of intersection representations
Chmel, Petr ; Jelínek, Vít (advisor) ; Kratochvíl, Jan (referee)
As some problems are (NP-)hard to solve in the general case, a possible approach is to try to solve the problem on a restricted class of graphs. In the thesis, we focus on graphs induced by axis-aligned L-shapes, so-called L-graphs, and a similar class of axis- aligned L-shapes and L-shapes, referred to as {L, L}-graphs, with two vertices sharing an edge if and only if their respective curves intersect. We show that recognizing both L- graphs and {L, L}-graphs is NP-complete. The second part of the thesis focuses on other typical decision problems on L-graphs and their relatives: finding the clique number, the independence number or a 3-coloring.
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CSP over oriented trees
Tatarko, William ; Bulín, Jakub (advisor) ; Barto, Libor (referee)
In this thesis we present an oriented tree with only 26 vertices, whose CSP is NP-complete. This serves as a counterexample for a conjecture that any oriented tree with this property has at least 39 vertices. The work itself is divided into three chapters. In the first one, basic definitions and tools of this topic are introduced. Then, tractability of trees of special shapes is shown. Finally, NP-completeness of a certain oriented tree is proven. 1
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