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Which of the following problems CANNOT be solved efficiently using the XOR self-cancellation pattern?

easy🔍 Pattern Recognition Q2 of Q15
Bit Manipulation - Single Number (XOR Self-Cancellation)
Which of the following problems CANNOT be solved efficiently using the XOR self-cancellation pattern?
AFind the two unique numbers in an array where every other element appears twice
BFind the element that appears only once when all others appear twice
CFind the majority element that appears more than half the time in an array
DFind the single number in an array where every other element appears twice
Step-by-Step Solution
Solution:

  1. Step 1: Analyze problem requirements

    Majority element requires counting frequency, not cancellation.

  2. Step 2: XOR pattern applicability

    XOR cancels pairs but cannot identify majority elements without counting.

  3. Final Answer:

    Option C -> Option C

  4. Quick Check:

    Majority element needs frequency counts, not XOR [OK]
Quick Trick: XOR can't find majority elements [OK]
Common Mistakes:
MISTAKES
  • Assuming XOR works for all unique element problems
  • Confusing majority with single unique element
Trap Explanation:
PITFALL
  • Candidates often think XOR solves all uniqueness problems, but majority element needs counting.
Interviewer Note:
CONTEXT
  • Tests anti-pattern recognition and problem suitability for XOR.
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