题目网址: www.puzzleup.com/2011/puzzle/?224 加分时限: 9/1 7PM - 9/6 7PM 答对可得基本分１００分。答案可上传５次，每改１次答案从基本分扣２０分。　 比赛期间内可随时上传答案，加分时限内答对第ｎ天加（６－ｎ）分　 　　 　　 另依题目的难易有额外加分（如有８０％的人这题答错，答对者加８０分）　　 ◆Chess Players 25 players are attending a chess tournament. In every possible combination of five players, at least one of the players has played with the other four players before. What is the minimum possible number of players in the tournament that has played with all the other 24 players before? 25个棋手参加一场西洋棋大赛。 任意选择五个棋手，总会至少有一人在之前和其他四人都对战过。 那麽这些人中最少有几个人和除自己之外的24人都对战过？ -- 又是图论题...= = -- 'You've sort of made up for it tonight,' said Harry. 'Getting the sword. Finishing the Horcrux. Saving my life.' 'That makes me sound a lot cooler then I was,' Ron mumbled. 'Stuff like that always sounds cooler then it really was,' said Harry. 'I've been trying to tell you that for years.' -- Harry Potter and the Deathly Hollows, P.308 --

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