Actually, Schik, we don't need recursion.
If Alice picks passenger #x's seat, then that passenger will have to sit in someone else's seat. So whoever that person is, #(x+y), will also be displaced, and will have to sit in someone else's seat. If we extrapolate this, it means that there will always be one person who is sitting in a seat that's not theirs, while the 'owner' of the seat hasn't come in yet. Thus, if Alice doesn't sit in her own seat, and Bob is #100, Bob will have to be displaced.
So, the odds of Bob taking his own seat are the odds that Alice will take her own seat. That's 1/100.
Matt
[Edited by Mattcrampy on 09-14-2004 at 04:24 AM GMT: Clarified reasoning]
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