Subsets & Combinations - Subsets Using Bitmask
Given the following code to generate subsets, what is the value of
result after processing num=2 when nums = [1, 2]?Given the following code to generate subsets, what is the value of result after processing num=2 when nums = [1, 2]?
easy🧾 Code Trace Q12 of Q15
Step-by-Step Solution
Step 1: Trace result after processing num=1
Initially result = [[]]. After num=1, new_subsets = [[1]], result = [[], [1]].Step 2: Trace result after processing num=2
For each subset in [[], [1]], add 2: new_subsets = [[2], [1, 2]]. Extend result: [[], [1], [2], [1, 2]].Final Answer:
Option D -> Option DQuick Check:
All subsets of [1,2] are present exactly once [OK]
Quick Trick: Iterative subsets double result size each iteration [OK]
Common Mistakes:
MISTAKES- Forgetting to add subsets with current num
- Appending duplicates
- Wrong order of subsets
Trap Explanation:
PITFALL- Confusing order or missing subsets leads to wrong result; careful iteration is key.
Interviewer Note:
CONTEXT- Tests ability to mentally execute iterative subset construction code.
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