Bit Manipulation - Single Number (XOR Self-Cancellation)
What is the output of the following code snippet when called with input [4, 1, 2, 1, 2]?
What is the output of the following code snippet when called with input [4, 1, 2, 1, 2]?
easy🧾 Code Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace XOR operations
0 · 4 = 4, 4 · 1 = 5, 5 · 2 = 7, 7 · 1 = 6, 6 · 2 = 4Step 2: Final result
The XOR of all elements is 4, the unique element.Final Answer:
Option A -> Option AQuick Check:
Result matches unique element 4 [OK]
Quick Trick: XOR all elements to isolate unique number [OK]
Common Mistakes:
MISTAKES- Miscounting XOR steps
- Off-by-one in loop
Trap Explanation:
PITFALL- Candidates often miscalculate XOR sequence or forget initial zero.
Interviewer Note:
CONTEXT- Tests ability to mentally execute XOR-based code.
Master "Single Number (XOR Self-Cancellation)" in Bit Manipulation
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