Creating all subsets recursively without using array in C language

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C

recursion

We get non negative integer number n from user and we must print all subsets of set ({1,2,3,...,n}).

for example for n=3 we must print:

{1 , 2 , 3}
{1 , 2}
{1 , 3}
{1}
{2 , 3}
{2}
{3}
{}
,s are optional and the sequence can be printed without any comma. (like {1 2 3}) I must add that the sequence of subsets must be exactly like the example. Meaning first the subsets that have 1, then subsets that have 2 and .... The longest subset must be printed first.

What I have tried:

I see a lot of codes in the Internet that solve this problem with arrays or using a bit array that indicate whether we use a number or not. The issue is that in this question, we are not allowed to use -any- type of array or other data structures like vector ,etc. Even using the array behaviour of something like string is completely prohibited. It must be solved only with recursion.

We are also not allowed to use any advanced functions. For example if we write it with C, we are allowed just to use stdio.h or for C++, only <iostream> is allowed and no other library.

I don't know how to do this without any arrays. How to check which number it must print and at the sametime, manage the {}.