Bit Manipulation - Power of Four
Suppose you need to check if a floating-point number x is an exact power of four (e.g., 4^k for integer k). Which approach would be most suitable?
Suppose you need to check if a floating-point number x is an exact power of four (e.g., 4^k for integer k). Which approach would be most suitable?
hard🎤 Interviewer Follow-up Q10 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand floating-point challenges
Bit manipulation on floats is complex and unreliable; iterative division requires integer input.Step 2: Consider logarithm approach
Floating point precision errors make exact equality checks unreliable, so use tolerance.Step 3: Use logarithm with tolerance
Check if log base 4 of x is close to an integer within a small epsilon.Final Answer:
Option B -> Option BQuick Check:
Logarithm with tolerance handles floating point precision issues [OK]
Quick Trick: Floating point needs tolerance or precomputed checks [OK]
Common Mistakes:
MISTAKES- Using direct bitmask on floats
- Assuming log equality is exact
Trap Explanation:
PITFALL- Candidates often apply integer bit tricks to floats incorrectly.
Interviewer Note:
CONTEXT- Tests handling of floating point variants and approach adaptation
Master "Power of Four" in Bit Manipulation
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