DMTCS Proceedings, 2005 European Conference on Combinatorics, Graph Theory and Applications (EuroComb '05)

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Balanced Avoidance Games on Random Graphs

Martin Marciniszyn, Dieter Mitsche, Miloš Stojaković

Abstract


We introduce and study balanced online graph avoidance games on the random graph process. The game is played by a player we call Painter. Edges of the complete graph with n vertices are revealed two at a time in a random order. In each move, Painter immediately and irrevocably decides on a balanced coloring of the new edge pair: either the first edge is colored red and the second one blue or vice versa. His goal is to avoid a monochromatic copy of a given fixed graph H in both colors for as long as possible. The game ends as soon as the first monochromatic copy of H has appeared. We show that the duration of the game is determined by a threshold function mH = mH(n). More precisely, Painter will asymptotically almost surely (a.a.s.) lose the game after m = ω(mH) edge pairs in the process. On the other hand, there is an essentially optimal strategy, that is, if the game lasts for m = o(mH) moves, then Painter will a.a.s. successfully avoid monochromatic copies of H using this strategy. Our attempt is to determine the threshold function for certain graph-theoretic structures, e.g., cycles.

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