I added the example. Is it clearer now?

Yes, pls: add the ouput example to the instructions. That would be helpful.

No, you need to return one dimensional array, and in such array position of a queen is for each x in (0 ... size), queen[x] = (x, returned_array[x]). So, for example, if you return array [1, 3, 0, 2], it means that there are 4 queens at coordinates:

[0, 1],
[1, 3],
[2, 0],
[3, 2]

Since in this problem each queen position has different x, we do not have to return it explicitly because it can be expressed as index in returned_array.

Is it clearer now? Maybe I should add such example to the description.