Bit Manipulation - Single Number III (Two Singles)
Consider this buggy code snippet for finding two unique numbers. Which line contains the subtle bug?
Consider this buggy code snippet for finding two unique numbers. Which line contains the subtle bug?
medium🐞 Bug Identification Q14 of Q15
Step-by-Step Solution
Step 1: Identify how set_bit is computed
Correct approach uses set_bit = xor & (-xor) to isolate rightmost set bit. Here, set_bit = xor misses this step.Step 2: Understand impact of bug
Without isolating rightmost set bit, partitioning fails, XOR groups won't separate unique numbers correctly.Final Answer:
Option A -> Option AQuick Check:
Bug in set_bit calculation breaks partitioning [OK]
Quick Trick: Isolate rightmost set bit with xor & (-xor) [OK]
Common Mistakes:
MISTAKES- Using xor directly as set_bit
- Breaking early before full XOR
- Misusing partition condition
Trap Explanation:
PITFALL- Using xor directly looks plausible but breaks partitioning logic subtly.
Interviewer Note:
CONTEXT- Tests if candidate spots subtle bit manipulation bug that breaks correctness.
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