Handshaking Lemma

Please comment your solutions, questions and remarks..

This one I learned from Sam Hardwick.

Show that the number of those, who have shaken their hands with others an odd number of times, is even.

Level 1/5

P.S. This lemma has deep applications. I’ll get back to it!

About Vadim Kulikov

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2 Responses to Handshaking Lemma

  1. Sam Hardwick says:

    This wording is slightly different and potentially misleading: “all of whom shake hands with each other” doesn’t mean eg. that everyone has shaken hands with everyone else. I think the problem is most elegant with the first sentence simply omitted.

  2. You are right. Thanks. I guess I wanted to emphasize that the size of the group doesn’t matter.

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