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AMC 10

Picture of Leo Zeng
Re: AMC 10
by Leo Zeng - Monday, December 14, 2020, 9:06 AM


What I've found out is that the most number of friends one person can have is 4, since they have the same number of friends. Also, the cases for 1 and 4 are the same, since for 4, you can take the cases for 1 and turn them into not-friends. Same for 2 and 3. So you have to first find out the cases for 1 and 2, then multiply by two.