s*****w
发帖数: 1527 | 1 > >> Part A:
> >>
> >> You are attending a fancy party. Upon arriving, each of the N
> >> partygoers (yourself included) puts his or her coat on the
> >> coatrack. After the party is over, the first person to leave is in
> >> a rush and grabs a coat at random from the coatrack. As the rest of
> >> the partygoers leave, they try to grab their own coat, but if their
> >> coat has already been taken, they take someone else's coat at
> >> random from the rack. You are the last person to leave the pa | h*****0
发帖数: 4889 | 2 A: 1/2
B: 1/(NP+1) (my guess :P)
【在 s*****w 的大作中提到】
: > >> Part A:
: > >>
: > >> You are attending a fancy party. Upon arriving, each of the N
: > >> partygoers (yourself included) puts his or her coat on the
: > >> coatrack. After the party is over, the first person to leave is in
: > >> a rush and grabs a coat at random from the coatrack. As the rest of
: > >> the partygoers leave, they try to grab their own coat, but if their
: > >> coat has already been taken, they take someone else's coat at
: > >> random from the rack. You are the last person to leave the pa
| s*****w
发帖数: 1527 | 3 my answer for A is 1/2 too,
how did you solve it pls ?
【在 h*****0 的大作中提到】
: A: 1/2
: B: 1/(NP+1) (my guess :P)
| j********e
发帖数: 30 | 4 这个版怎么还不改名为“概率”版呢？
【在 s*****w 的大作中提到】
: my answer for A is 1/2 too,
: how did you solve it pls ?
| S*********g
发帖数: 5298 | 5 when P=1, it should be 1/N
【在 h*****0 的大作中提到】
: A: 1/2
: B: 1/(NP+1) (my guess :P)
| h*****0
发帖数: 4889 | 6 P=1 equivalant to P = (N-1)/N
my formula only works for P <= (N-1)/N
【在 S*********g 的大作中提到】
: when P=1, it should be 1/N
| S*********g
发帖数: 5298 | 7 your formula is correct.
let us assume there are m drunk persons, who will take a hat randomly.
Here, 0<= m < N
Let us assume their own hats have indices x1
when the first drunk guy takes a hat,
x1,x2,...,xm and N(your hat) has the same probability to be taken.
(a) if he takes one of x1,x2,...,xm,
then the probablem reduces to a problem of (m-1) drunk guy
(b) if he takes your hat,
you have zero chance to get it
(c) otherwise, if he takes x's hat,
x's becomes the new
【在 h*****0 的大作中提到】
: P=1 equivalant to P = (N-1)/N
: my formula only works for P <= (N-1)/N
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