Probability of taking seats

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Assume n people who are initially assigned seats from 1 t0 n but they don't know their seat number, now they randomly pick up a seat on their own and what would be the probability that no one is seating to its assigned seat?

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These permutations, where no element is mapped to itself, are known as Derangements. You get the probability by dividing by the number of all permutations. So it is

$$\frac{\left\lfloor\frac{n!}{e}+\frac{1}{2}\right\rfloor}{n!}.$$

(This most certainly is a duplicate but I couldn't find any post that had just this basic derangment question).