Hi everyone I was solving [this problem](https://www.hackerrank.com/contests/goc-cdc-series-7/challenges/different-chocolates/problem). I tried a lot for finding a general formula for — How many permutation out of $n!$ will lead to exactly $K$ different chocolates. Then we just have to find probability by dividing with $n!$ and find Expectation by multiplying with $K$ and finally add the expectation for all such $K$ in range $[1,N]$.↵
But I am unable to find a general formula for this. Also I am not able to get the editorial basically proof of that. ↵
Can anyone please provide some idea regarding this. It'll be of great help.
But I am unable to find a general formula for this. Also I am not able to get the editorial basically proof of that. ↵
Can anyone please provide some idea regarding this. It'll be of great help.