Subsets - Bitmask Approach

The idea: with $n$ elements, there are $2^n$ subsets. Loop through all integers from $0$ to $2^n - 1$, treating each as a bitmask.

For each mask, build a subset by including element $i$ if bit $i$ is set. For $[1,2,3]$ and mask $5 = 101$, bits 0 and 2 are set, so the subset is $[1, 3]$.

This works because it directly maps the binary representation of numbers to subsets. No recursion needed.