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China Mathematical Olympiad 1987 problem3

Source: China Mathematical Olympiad 1987 problem3

January 7, 2014
combinatorics unsolvedcombinatorics

Problem Statement

Some players participate in a competition. Suppose that each player plays one game against every other player and there is no draw game in the competition. Player AA is regarded as an excellent player if the following condition is satisfied: for any other player BB, either AA beats BB or there exists another player CC such that CC beats BB and AA beats CC. It is known that there is only one excellent player in the end, prove that this player beats all other players.