use recursion to generate random permutations

a) Write a recursive algorithm that takes as input a set of elements and an integer l, and returns all their permutations of length l.

b) Adjust the previous algorithm to return a random subset of all the permutations containing n elements.

Hint: generating all the permutations and selecting n of them afterwards in not a good idea.

a) and b) are two codes.I really don't know how to write the code. Any help will be appreciated! Thanks a lot!

Answer 1

[Ameer Hamza]

See nchoosek(): https://www.mathworks.com/help/matlab/ref/nchoosek.html

[越琪 吴]

Thanks!