Bit Manipulation - Power of Two
Suppose you want to check if a number is a power of two but the input can be negative or zero, and you want to handle 64-bit integers efficiently. Which modification to the bit manipulation approach is correct?
Which modification to the bit manipulation approach is correct?
hard🎤 Interviewer Follow-up Q15 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand input constraints
Negative and zero inputs are not powers of two, so must be excluded explicitly.Step 2: Apply correct bit manipulation check
Check n > 0 first, then use n & (n - 1) == 0 to verify exactly one set bit.Step 3: Confirm correctness for 64-bit integers
This approach works efficiently for 64-bit integers as well, since bitwise ops are constant time.Final Answer:
Option A -> Option AQuick Check:
Explicit positive check avoids errors on zero/negative inputs [OK]
Quick Trick: Always check n > 0 before bitwise power-of-two test [OK]
Common Mistakes:
MISTAKES- Using incorrect bitwise operations
- Ignoring negative inputs
- Using floating point logs causing precision errors
Trap Explanation:
PITFALL- Some think bitwise trick works for all integers without input validation, which is false.
Interviewer Note:
CONTEXT- Tests candidate's ability to adapt solutions to input constraints and data types.
Master "Power of Two" in Bit Manipulation
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