
Twinless articulation points and some related problems
Let G=(V,E) be a twinless strongly connected graph. a vertex v∈ V is a t...
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Counting orientations of graphs with no strongly connected tournaments
Let S_k(n) be the maximum number of orientations of an nvertex graph G ...
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2blocks in strongly biconnected directed graphs
A directed graph G=(V,E) is called strongly biconnected if G is strongly...
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Strengthening neighbourhood substitution
Domain reduction is an essential tool for solving the constraint satisfa...
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Safe sets in digraphs
A nonempty subset S of the vertices of a digraph D is called a safe se...
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Parameterized Complexity of MinPower Asymmetric Connectivity
We investigate parameterized algorithms for the NPhard problem MinPowe...
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P not equal to NP
Let G(V,E) be a graph with vertex set V and edge set E, and let X be eit...
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QCSP on Reflexive Tournaments
We give a complexity dichotomy for the Quantified Constraint Satisfaction Problem QCSP(H) when H is a reflexive tournament. It is wellknown that reflexive tournaments can be split into a sequence of strongly connected components H_1,...,H_n so that there exists an edge from every vertex of H_i to every vertex of H_j if and only if i<j. We prove that if H has both its initial and final strongly connected component (possibly equal) of size 1, then QCSP(H) is in NL and otherwise QCSP(H) is NPhard.
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