Problem

Given a set of distinct integers, return all possible subsets.
Example input: [1,2,3]
Example output:
[
  [1],
  [2],
  [3],
  [1,2],
  [1,3],
  [2,3],
  [1,2,3]
]

Solution

# Solution:
# The solution is to use a recursive function that takes in a list of integers and a list of lists.
# The function will iterate through the list of integers and add each integer to the list of lists.
# Then it will call itself with the list of integers minus the current integer and the list of lists.
# This will continue until the list of integers is empty.
# The function will then return the list of lists.
# This solution is optimal because it is O(2^n) time complexity and O(n) space complexity.

def subsets(nums):
    return subsets_helper(nums, [])

def subsets_helper(nums, lists):
    if len(nums) == 0:
        return lists
    else:
        for i in range(len(nums)):
            lists.append([nums[i]])
            lists = subsets_helper(nums[i+1:], lists)
        return lists

print(subsets([1,2,3]))