Answer
We can do this recursively.
Work Step by Step
We can do this recursively, which means reducing a problem to a smaller instance of the same problem. Suppose that the elements of the set in question are listed: A= { a1, a2, a3, ... , a,,}. First we will write down all the subsets that do not involve a,,. This is just the same problem we are talking about all over again, but with a smaller set---one with just n - 1 elements. We do this by the process we are currently describing. Then we write these same subsets down again, but this time adjoin a,, to each one. Each subset of A will have been written down, then-first all those that do not include a,,, and then all those that do.
For example, using this procedure the subsets of {p, d, q} would be listed in the order 0, {p} , { d} ,
{p,d}, {q}, {p,q}, {d,q}, {p,d,q}.
