Social Golfer Problem

Twenty golfers wish to play in foursomes for 5 days. Is it possible for each golfer to play no more than once with any other golfer? The answer is yes, and the following table gives a solution. Mon ABCD EFGH IJKL MNOP QRST Tue AEIM BJOQ CHNT DGLS FKPR Wed AGKO BIPT CFMS DHJR ELNQ Thu AHLP BKNS CEOR DFIQ GJMT Fri AFJN BLMR CGPQ DEKT HIOS Event organizers for bowling, golf, bridge, or tennis frequently tackle problems of this sort, unaware of the problem complexity. In general, it is an...