Bit Manipulation - Power of Four
If the input number n can be negative or zero, and you want to check if its absolute value is a power of four, which modification to the optimal logarithm-based approach is correct?
If the input number n can be negative or zero, and you want to check if its absolute value is a power of four, which modification to the optimal logarithm-based approach is correct?
hard🎤 Interviewer Follow-up Q15 of Q15
Step-by-Step Solution
Solution:
Step 1: Consider input domain
Since n can be zero or negative, these are not powers of four, so must return False immediately.Step 2: Apply logarithm check on absolute value
After filtering invalid inputs, apply logarithm on abs(n) to check power of four.Step 3: Finalize correct approach
Adding a check to return False for zero or negative inputs before log check ensures correctness and avoids math domain errors.Final Answer:
Option B -> Option BQuick Check:
Zero and negatives are filtered out before log check on abs(n) [OK]
Quick Trick: Filter invalid inputs before log check on abs(n)
Common Mistakes:
MISTAKES- Removing input validation
- Applying log on negative numbers causing errors
Trap Explanation:
PITFALL- Taking abs without filtering zero or negatives causes math domain errors or incorrect results.
Interviewer Note:
CONTEXT- Tests candidate's ability to adapt solution to relaxed constraints and handle edge cases robustly.
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