I need a function like this:
// return true iff 'n' is a power of 2, e.g. // is_power_of_2(16) => true is_power_of_2(3) => false bool is_power_of_2(int n);
Can anyone suggest how I could write this? Can you tell me a good web site where this sort of algorithm can be found?
(n & (n - 1)) == 0 is best. However, note that it will incorrectly return true for n=0, so if that is possible, you will want to check for it explicitly.
http://www.graphics.stanford.edu/~seander/bithacks.html has a large collection of clever bit-twiddling algorithms, including this one.