Pavel Valtr

  1. Graph sharing games: complexity and connectivity.

    Authors: Josef Cibulka, Pavel Valtr, Jan Kynčl, Viola Mészáros, Rudolf Stolař
    Subjects: Discrete Mathematics
    Abstract

    We study the following combinatorial game played by two players, Alice and
    Bob, which generalizes the Pizza game considered by Brown, Winkler and others.
    Given a connected graph G with nonnegative weights assigned to its vertices,
    the players alternately take one vertex of G in each turn. The first turn is
    Alice's. The vertices are to be taken according to one (or both) of the
    following two rules: (T) the subgraph of G induced by the taken vertices is
    connected during the whole game, (R) the subgraph of G induced by the remaining
    vertices is connected during the whole game.

  2. On empty pentagons and hexagons in planar point sets.

    Authors: Pavel Valtr
    Subjects: Combinatorics
    Abstract

    We give improved lower bounds on the minimum number of $k$-holes (empty
    convex $k$-gons) in a set of $n$ points in general position in the plane, for
    $k=5,6$.

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