random vector containing zero and values

I have an problem: I have a vector A with size N; I want to fill it up with a random vector with values from [1 randi(N)] while the other elements of A be zero. for example:

    N = 6;
    A(1:6)=0;
    b = randi(N);
    C =randperm(b);

now without any loop assign each element of C to the random positions of A while the other un-assigned elements of A remain zero if b<N;

Answer 1

[Adam]

a = zeros(1,6);
n = 6;
b = randi(n);
c = 1:b;

a( randperm( numel(a), b ) ) = c;

Answer 2

[Alexandra Harkai]

A(1:6)=0;
N = 6;
b = randi(N);
C =(1:b);
A_idx = randperm(N, b); % generate b random integers from 1 to N
C_idx = randperm(b); % generate a random permutation of integers from 1 to b
A(A_idx) = C(C_idx); % assign values according to the indices

[Alexandra Harkai]

I realised I over-complicated this by making it random in A and C, but there's no need to. :)

[meh alipoo]

This is also the answer. Thank you.