How to check if a number is a power of 2

Question

Today I needed a simple algorithm for checking if a number is a power of 2.

The algorithm needs to be:

1. Simple
2. Correct for any ulong

Answer 1

Here's a simple C++ solution:

bool IsPowerOfTwo( unsigned int i )
{
    return std::bitset<32>(i).count() == 1;
}