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You need to determine if a given positive integer n is a power of four. Which algorithmic pattern best fits this problem?

easy🔍 Pattern Recognition Q1 of Q15
Bit Manipulation - Power of Four
You need to determine if a given positive integer n is a power of four. Which algorithmic pattern best fits this problem?
ASliding window to find subarrays with a given sum
BDynamic programming for subset sum problems
CBit manipulation to check single set bit and bitmask positions
DTwo pointers to find pairs with a specific difference
Step-by-Step Solution
Solution:
  1. Step 1: Understand the problem requires checking if n = 4^k

    This means n must have exactly one set bit and that bit must be at an even position (0-based).
  2. Step 2: Recognize bit manipulation pattern

    Checking single set bit and using a mask like 0x55555555 to ensure the bit is at an even position is the key approach.
  3. Final Answer:

    Option C -> Option C
  4. Quick Check:

    Power of four check uses bitmask and single bit test [OK]
Quick Trick: Power of four requires single set bit at even position [OK]
Common Mistakes:
MISTAKES
  • Confusing power of two with power of four
  • Using loops instead of bitmask
Trap Explanation:
PITFALL
  • Many candidates think checking single set bit is enough, missing the even position bitmask.
Interviewer Note:
CONTEXT
  • Tests candidate's ability to recognize bit manipulation pattern for power checks
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