Bit Manipulation - Single Number (XOR Self-Cancellation)
Suppose the input array can contain multiple elements that appear only once, while all others appear twice. Which modification to the XOR approach correctly finds all unique elements?
Suppose the input array can contain multiple elements that appear only once, while all others appear twice. Which modification to the XOR approach correctly finds all unique elements?
hard🎤 Interviewer Follow-up Q15 of Q15
Step-by-Step Solution
Step 1: Understand XOR limitation
XOR of multiple unique elements combined is a single number, not individual uniques.Step 2: Identify approach to find all unique elements
Counting occurrences with a hash map correctly identifies all unique elements.Step 3: Compare alternatives
Sorting works but is less efficient; recursive XOR splitting is complex and error-prone.Final Answer:
Option C -> Option CQuick Check:
Hash map approach correctly handles multiple unique elements [OK]
Quick Trick: XOR only isolates one unique element, not multiple [OK]
Common Mistakes:
MISTAKES- Assuming XOR returns all unique elements
- Ignoring multiple unique elements case
- Overcomplicating with recursion
Trap Explanation:
PITFALL- XOR approach is optimal only for exactly one unique element; multiple uniques require counting.
Interviewer Note:
CONTEXT- Tests candidate's understanding of XOR approach limitations and ability to adapt solutions.
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