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Which approach correctly adapts to count the number of max bitwise-OR subsets under this new constraint?

hard🎤 Interviewer Follow-up Q15 of Q15
Subsets & Combinations - Count Number of Max Bitwise-OR Subsets
Suppose the problem is modified so that elements can be chosen multiple times (unlimited reuse) to form subsets. Which approach correctly adapts to count the number of max bitwise-OR subsets under this new constraint?
AUse dynamic programming over OR values with state compression to count combinations
BUse backtracking with memoization to handle repeated elements and prune search
CUse the same bitmask enumeration approach since subsets remain finite
DSort elements and greedily pick those with highest bits until max OR is reached
Step-by-Step Solution
  1. Step 1: Recognize infinite subsets due to unlimited reuse

    Bitmask enumeration is infeasible as subsets are infinite with reuse allowed.
  2. Step 2: Use DP over OR states to count combinations efficiently

    DP with state compression tracks counts of subsets achieving each OR value, handling reuse.
  3. Step 3: Understand greedy or naive backtracking fail due to infinite or redundant subsets

    Greedy misses combinations; naive backtracking is exponential and inefficient.
  4. Final Answer:

    Option A -> Option A
  5. Quick Check:

    DP over OR states handles reuse -> correct and efficient [OK]
Quick Trick: Reuse means infinite subsets -> DP over OR states needed [OK]
Common Mistakes:
MISTAKES
  • Trying bitmask enumeration despite infinite subsets
  • Using greedy approach ignoring subset counts
Trap Explanation:
PITFALL
  • Naive reuse handling looks similar but breaks due to infinite subsets, requiring DP.
Interviewer Note:
CONTEXT
  • Tests candidate's ability to adapt solutions to problem variants with reuse and infinite subsets.
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