Given the following Python code that generates all subsets of nums = [1, 2, 3], what is the value of res after the function completes?

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Bit Manipulation - Subsets Using Bitmask

Given the following Python code that generates all subsets of nums = [1, 2, 3], what is the value of res after the function completes?

A[[], [1], [1, 2], [1, 2, 3], [1, 3], [2], [2, 3], [3]]

B[[], [1], [2], [3], [1, 2], [1, 3], [2, 3], [1, 2, 3]]

C[[], [3], [2], [2, 3], [1], [1, 3], [1, 2], [1, 2, 3]]

D[[], [1], [1, 3], [1, 2], [1, 2, 3], [2], [2, 3], [3]]

Step-by-Step Solution

Solution:

Step 1: Trace backtrack calls and subsets added
Initially, empty subset [] is added. Then 1 is added, subsets with 1 are generated, then 2, then 3, backtracking after each.
Step 2: Confirm order and completeness of subsets
Subsets are generated in lexicographic order due to sorting and incremental indices: [], [1], [1,2], [1,2,3], [1,3], [2], [2,3], [3].
Final Answer:
Option A -> Option A
Quick Check:
Matches expected subsets order from backtracking [OK]

Quick Trick: Backtracking adds subsets in sorted order [OK]

Common Mistakes:

MISTAKES

Trap Explanation:

PITFALL

Some candidates expect subsets in sorted order by size or lex order, but backtracking order differs slightly.

Interviewer Note:

CONTEXT

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