"""
Generates all subsets
"""
import sys


# def is_solution(k, n):
#     return k == n
#
#
# def construct_candidates():
#     return [0, 1]
#
#
# def process_solution(working_set):
#     global solutions
#
#     s = {k for k in working_set if working_set[k] == 1}
#     solutions.append(s)
#
#
# def backtrack(working_set, k, n):
#
#     if is_solution(k, n):
#         process_solution(working_set)
#     else:
#         k += 1
#         candidates = construct_candidates()
#         for i in candidates:
#             working_set[k] = i
#             backtrack(working_set, k, n)


def backtrack_compact(working_set, k, n):
    global solutions

    if k == n:
        s = {k for k in working_set if working_set[k] == 1}
        solutions.append(s)
    else:
        k += 1
        for i in [0, 1]:
            working_set[k] = i
            backtrack_compact(working_set, k, n)


def main():
    if 0 < 1 < len(sys.argv):
        n = int(sys.argv[1])
    else:
        exit('Usage: subsets.py number')

    global solutions
    solutions = []

    # backtrack({}, 0, n)
    # print(solutions)

    backtrack_compact({}, 0, n)
    print(solutions)
    print('Number of subsets: {}'.format(len(solutions)))


if __name__ == '__main__':
    main()