Bit Manipulation - Subsets Using Bitmask
Given the following bitmask enumeration code for subsets, what is the output when nums = [1, 2]?
Given the following bitmask enumeration code for subsets, what is the output when nums = [1, 2]?
easy🧾 Code Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace mask values for n=2
mask=0 -> [], mask=1 -> [1], mask=2 -> [2], mask=3 -> [1,2]Step 2: Confirm output order
Subsets appended in order of mask from 0 to 3, matching [[], [1], [2], [1, 2]].Final Answer:
Option B -> Option BQuick Check:
Output matches expected subsets in ascending mask order [OK]
Quick Trick: Mask 0 means empty subset, increasing mask adds elements [OK]
Common Mistakes:
MISTAKES- Confusing mask bit order
- Misordering subsets in output
Trap Explanation:
PITFALL- Candidates often confuse bit order or subset order, leading to wrong output choices.
Interviewer Note:
CONTEXT- Tests candidate's ability to mentally execute bitmask subset generation.
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