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Consider two approaches to generate all subsets: (1) backtracking with for-loop iterating from start index, and (2) bit manipulation iterating over masks. When is approach (1) preferable over (2)?

hard⚖️ Approach Comparison Q8 of Q15
Subsets & Combinations - Subsets
Consider two approaches to generate all subsets: (1) backtracking with for-loop iterating from start index, and (2) bit manipulation iterating over masks. When is approach (1) preferable over (2)?
AWhen subsets need to be generated with early pruning or constraints
BWhen subsets must be generated in lexicographical order
CWhen input size n is very large (e.g., >30)
DWhen memory usage must be minimized
Step-by-Step Solution
Solution:

  1. Step 1: Compare approaches

    Bit manipulation enumerates all subsets blindly; backtracking can prune search space.

  2. Step 2: Identify scenarios benefiting from pruning

    Backtracking with for-loop allows early pruning based on constraints, making it preferable.

  3. Final Answer:

    Option A -> Option A

  4. Quick Check:

    Backtracking supports pruning; bitmask does not [OK]
Quick Trick: Backtracking allows pruning; bitmask does not [OK]
Common Mistakes:
MISTAKES
  • Assuming bitmask is always faster
  • Ignoring pruning benefits
Trap Explanation:
PITFALL
  • Candidates often overlook pruning advantages of backtracking, favoring bitmask for all cases.
Interviewer Note:
CONTEXT
  • Tests tradeoff reasoning between subset generation methods
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