Practice: Subsets

Problem: https://leetcode.com/problems/subsets/

Recognition reminder: you are asked to generate every subset of the input, the full power set. “Generate all” is the backtracking cue. Each element is a binary choice (in or out), and because a set has no order, [1, 2] and [2, 1] are the same subset, so you only ever look forward from the element you are on.

Before you start (the five-beat rhythm)

  1. Your Pattern Card for this week is already written.
  2. Name the pattern aloud and write your approach as a plain-English comment before any code.
  3. Struggle floor: 25 minutes unaided. No hints, no AI, no Discuss tab.
  4. If stuck past the floor, ask the tutor for a hint. Six rungs, one per ask.
  5. Debrief in your commit message before moving to the next problem.

Your target

Fill these in yourself before you look at anyone else’s solution:

Target time complexity:  ____
Target space complexity: ____

There are 2^n subsets, and each one must be copied into the result. Let that guide your time target, and remember that the recursion stack and the running path are separate from the output you must return.

Where your code goes

Write your solution in your own work repo (see getting-started.md), not in this folder. This folder ships only the problem spec and a provided-example test (tests/test_provided.py) so you can check the given cases locally before you submit to LeetCode’s judge. The judge is the oracle; the tutor will not confirm your answer by reading it.

Note on the test: subsets may be returned in any order, and the order of elements inside each subset does not matter either, so the provided test normalizes both sides (it sorts within each subset, then sorts the list of subsets) before comparing. Do not rely on producing them in any particular order.

Debrief (paste into your commit message) 

1. What pattern did this turn out to be?
2. What was the trigger phrase or input shape that should have made me reach for it?
3. What was the time and space complexity, and what would dominate at scale?
4. What edge case would have broken my first attempt?
5. What would I do differently in three days when I see this cold?