The other day I asked:
So ... I know you've all been working on the problem ... want to know the answer? No, it's not 42, it's ... Here's how I got it. Basically each person can either stay where they are or swap with the person next to them. If they don't stay where they are and don't swap, then you end up with an unused chair and someone who has no chair, and that's not allowed. Let's first consider a table which is NOT round. Let's call N(x) the number of ways people can be reseated at such a table, where x is the total number of people and seats. The first person can either stay where they are, or they can swap with their only neighbor. If they stay where they are, there are N(x-1) remaining possibilities. If they swap, there are Next lets consider a table which IS round. Let's call R(x) the number of ways people can be reseated at such a table, where x is the total number of people and seats. The first person either stays where they are, or they can swap with their left neighbor, or swap with their right neighbor. If they stay where they are, there are Okay... now we can solve the problem:
Bon appetit! * after the first person decides, the rest of the round table becomes "straight" |
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