Finding all the subsets of a set

It's very simple to do this recursively. The basic idea is that for each element, the set of subsets can be divided equally into those that contain that element and those that don't, and those two sets are otherwise equal.

• For n=1, the set of subsets is {{}, {1}}
• For n>1, find the set of subsets of 1,...,n-1 and make two copies of it. For one of them, add n to each subset. Then take the union of the two copies.

Edit To make it crystal clear:

• The set of subsets of {1} is {{}, {1}}
• For {1, 2}, take {{}, {1}}, add 2 to each subset to get {{2}, {1, 2}} and take the union with {{}, {1}} to get {{}, {1}, {2}, {1, 2}}
• Repeat till you reach n

Too late to answer, but an iterative approach sounds easy here:

1) for a set of n elements, get the value of 2^n. There will be 2^n no.of subsets. (2^n because each element can be either present(1) or absent(0). So for n elements there will be 2^n subsets. ). Eg:
for 3 elements, say {a,b,c}, there will be 2^3=8 subsets

2) Get a binary representation of 2^n. Eg:
8 in binary is 1000

3) Go from 0 to (2^n - 1). In each iteration, for each 1 in the binary representation, form a subset with elements that correspond to the index of that 1 in the binary representation. Eg:

For the elements {a, b, c}
000 will give    {}
001 will give    {c}
010 will give    {b}
011 will give    {b, c}
100 will give    {a}
101 will give    {a, c}
110 will give    {a, b}
111 will give    {a, b, c}

4) Do a union of all the subsets thus found in step 3. Return. Eg:
Simple union of above sets!