Sorry, but it's not clear to me what the objective is. At test #3, nchoosek should accept a v that is a cell array of 30 column vectors? (What's the purpose: to present combinations per vector, or to present all cell arrays that choose a certain number of vectors?) And at test #4, nchoosek(v,1) should equal v', even when v contains duplicate entries and isn't sorted?

nchoosekFast(V,K) should have the same behavior as nchoosek(V,K) for a vector V.
you can valid:
celldisp(nchoosek({[1 2],[5 6 7],3}, 2)),
nchoosek([3 1 2 2], 1).

Always return "While evaluating the solution, the server encountered an error caused by temporary unavailability of MATLAB Service. Wait a few minutes for the MATLAB Service to return, and then rescore."