Power of Two

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Question

Approach

I used a bitwise trick. A number is a power of two if:

• It is positive.
• It has exactly one bit set in its binary representation.

The property (n & (n - 1)) == 0 checks this, because subtracting 1 from a power of two flips the single 1 bit to 0 and sets all lower bits to 1, so the bitwise AND becomes 0. For any number that isn’t a power of two, this condition fails.

Implementation

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        return n > 0 and (n & (n - 1)) == 0

Complexities

• Time: O(1)
• Space: O(1)