Building an arithmetic progression in a game
Source: Finland 2011, Problem 5
May 5, 2013
arithmetic sequencecombinatorics unsolvedcombinatorics
Problem Statement
Two players, the builder and the destroyer, plays the following game. Builder starts and players chooses alternatively different elements from the set Builder wins if some four integer of those six integer he chose forms an arithmetic sequence. Destroyer wins if he can prevent to form such an arithmetic four-tuple. Which one has a winning strategy?