Power of Two - Implementation

Here is the complete solution:

function isPowerOfTwo(n)
    return n > 0 and (n & (n - 1)) = 0

The check $n > 0$ excludes zero and negative numbers. The expression $n \& (n - 1) = 0$ ensures exactly one 1 bit. Time: $O(1)$. Space: $O(1)$. This bit trick replaces a loop with a single operation.