247 research outputs found

    Generating random graphs in biased Maker-Breaker games

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    We present a general approach connecting biased Maker-Breaker games and problems about local resilience in random graphs. We utilize this approach to prove new results and also to derive some known results about biased Maker-Breaker games. In particular, we show that for b=o(n)b=o\left(\sqrt{n}\right), Maker can build a pancyclic graph (that is, a graph that contains cycles of every possible length) while playing a (1:b)(1:b) game on E(Kn)E(K_n). As another application, we show that for b=Θ(n/lnn)b=\Theta\left(n/\ln n\right), playing a (1:b)(1:b) game on E(Kn)E(K_n), Maker can build a graph which contains copies of all spanning trees having maximum degree Δ=O(1)\Delta=O(1) with a bare path of linear length (a bare path in a tree TT is a path with all interior vertices of degree exactly two in TT)

    Notes on a conjecture of Manoussakis concerning Hamilton cycles in digraphs

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    In 1992, Manoussakis conjectured that a strongly 2-connected digraph DD on nn vertices is hamiltonian if for every two distinct pairs of independent vertices x,yx,y and w,zw,z we have d(x)+d(y)+d(w)+d(z)4n3d(x)+d(y)+d(w)+d(z)\geq 4n-3. In this note we show that DD has a Hamilton path, which gives an affirmative evidence supporting this conjecture.Comment: 8 page

    A Note on Long non-Hamiltonian Cycles in One Class of Digraphs

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    Let DD be a strong digraph on n4n\geq 4 vertices. In [3, Discrete Applied Math., 95 (1999) 77-87)], J. Bang-Jensen, Y. Guo and A. Yeo proved the following theorem: if (*) d(x)+d(y)2n1d(x)+d(y)\geq 2n-1 and min{d+(x)+d(y),d(x)+d+(y)}n1min \{d^+(x)+ d^-(y),d^-(x)+ d^+(y)\}\geq n-1 for every pair of non-adjacent vertices x,yx, y with a common in-neighbour or a common out-neighbour, then DD is hamiltonian. In this note we show that: if DD is not directed cycle and satisfies the condition (*), then DD contains a cycle of length n1n-1 or n2n-2.Comment: 7 pages. arXiv admin note: substantial text overlap with arXiv:1207.564
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