How to generate the power-set of a given List?

Question

I\'m trying to generate a collection of all 2^N - 1 possible combinations of a given List of length N. The collection will map the number of elements in a combination to an

Answer 1

What you're asking is generating all possible subsets of a set. You can think of it as iterating over all possible binary arrays of size N (the size of your list):

000000...000
000000...001
000000...010
000000...011
etc.

Why is that? The answer is simple: 1 indicates that an element exists in a subset, while 0 indicates that it is absent.

So, the basic algorithm is obvious:

s = [A, B, C, D]

for i=0 to 2^N-1:
   b = convert_number_to_bin_array(i)
   ss = calculate_subset_based_on_bin_array(s, b)
   print ss

Where calculate_subset_based_on_bin_array iterates on b and s and selects elements from s[current] where b[current] = 1.

The above will print out all existing subsets. You can adapt this algorithm in order to get the map that you've asked for in your question.