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Playing on a convex n-agon and winning strategies

Source: Rioplatense Olympiad 2013, Level 3, Problem 4

August 23, 2014
inductioncombinatoricsgamegame strategy

Problem Statement

Two players AA and BB play alternatively in a convex polygon with n5n \geq 5 sides. In each turn, the corresponding player has to draw a diagonal that does not cut inside the polygon previously drawn diagonals. A player loses if after his turn, one quadrilateral is formed such that its two diagonals are not drawn. AA starts the game. For each positive integer nn, find a winning strategy for one of the players.