How to pick the elements in a vector with row coordinates satisfying a criterion determined by another vector?

Hi, I have a column vector A reporting the first m natural numbers, each of them repeated an arbitrary number of times, e.g.

A=[1;1;2;2;2;3;4;4;4;4];

and a column vector B reporting the first n natural numbers, n>=m, each of them repeated an arbitrary number of times, e.g.

B=[1;2;3;3;3;4;5;5;6;7];

I want to obtain a column vector C reporting the elements of B with row coordinates equal to the row coordinates of each natural number last repetition in A. In the example:

C=[B(2);B(5); B(6); B(10)];

Answer 1

[Andrei Bobrov]

[ii,ii]=unique(A,'last');
C = B(ii);

Answer 2

[Roger Stafford]

 C = B(find([diff(A)~=0,true]));

Note that for this to work, B should have at least as many elements as A.