shortest way to check if a positive integer is a power of two

Question

This question is from job interview...
Use this template to write a C++ function that checks if a positive integer is a power of two.

bool p(int n)
{
    return ********;
}

You have to replace the 8 '*' symbols with other symbols in order to make the function work correctly.
My best approach was this:

bool p(int n)
{
    return !(n&=n-1);
}

Unfortunately it was wrong, because there are 9 symbols here...
Any ideas?

https://graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2 — sehe, Oct 30 '15 at 23:43

LogicStuff · Accepted Answer · 2015-10-30T22:15:43.833

0

Why assign to n? Just remove = and you have one character less. It will create a temporary instead, the logic won't change.

edited Oct 30 '15 at 22:15

answered Oct 30 '15 at 21:51

LogicStuff

well, I thought '&' had a higher priority than '-' Thank you! – delta-terminator Oct 30 '15 at 21:57
Then replace that eight stars with call to the function from the duplicate :) – LogicStuff Oct 30 '15 at 22:04
@John Devou No, [bitwise AND is below binary minus](http://en.cppreference.com/w/cpp/language/operator_precedence). – LogicStuff Oct 30 '15 at 22:14

1 Answers1