Knight Party

Oh right, I have a blog I'm supposed to maintain. All sorts of new puzzles these days, means I will proably forget them all before I manage to post them.

So, this is a knights and knaves puzzle, which I have in the past said I don't like, but I keep finding interesting ones (for those that don't recall, "knights" are people who always tell the truth, and "knaves" are people who always lie, not that that is actaully relevant for this puzzle, but it sets the tone a bit).

I got this puzzle from Presh Talwalkar's YouTube channel:
There is a party with 100 people, and each person is either a truth teller or a lair. At the party, some of the people may shake hands with eachother, and after the party you ask each person "How many truth tellers did you shake hands with?". The people each give a different answer, with each integer from 0 to 99 appearing as an answer.

How many truth tellers are at the party?

Naturaly, you can take it as given that if A shakes hands with B, then B also shook hands with A, you may also assume that nobody can shake hands with themselves. It is possible that everybody shook hands with everybody else, or simply that there were no handshakes, or anything in between of course. The solution is nothing special, but it is a nice logical solution.

2 comments:

Anonymous said...

Can A shake hands with A? ;-)

Kory Stevens said...

No, nobody can shake hands with themselves. I had intended that to be part of my clarification, but I guess I forgot, I will edit the post.