h*******i
发帖数: 11 | 1 This is a phone interview problem for a quant position.
There are infinite number of boxes, within each box there is a ball. The
balls have 4 possible different colors(equal probabilities). The question is
what is the expected number of boxes that one has to open to have a full
collection of balls with all 4 different colors.
I know how to solve this by constructing a MC. Anyone knows a quick way,
since this is just a phone interview problem? Thanks a lot... |
z****i
发帖数: 406 | 2 coupon collection problem?
1+4/3+4/2+4/1 |
k*******d
发帖数: 1340 | |
h*******i
发帖数: 11 | 4 Appreciate it, guys...Good luck |
o******e
发帖数: 1001 | 5 也可以用markov chain做，
令1，2，3，4为收集到球的不同color的数目，建立markov chain,计算从state 1到4的
期望步数。答案是25/3.
is
【在 h*******i 的大作中提到】
: This is a phone interview problem for a quant position.
: There are infinite number of boxes, within each box there is a ball. The
: balls have 4 possible different colors(equal probabilities). The question is
: what is the expected number of boxes that one has to open to have a full
: collection of balls with all 4 different colors.
: I know how to solve this by constructing a MC. Anyone knows a quick way,
: since this is just a phone interview problem? Thanks a lot...
|
