Question

Which of these expressions will return true if the input integer v is a power of two?

(a) (v | (v + 1)) == 0;

(b) (~v & (v – 1)) == 0;

(c) (v | (v – 1)) == 0;

(d) (v & (v – 1)) == 0;

I got this question in an international level competition.

The query is from Integer Types topic in portion Types, Pointers, Arrays & Structures in C++ of C++

Answer 1

Right answer is (d) (v & (v – 1)) == 0;

Explanation: Power of two integers have a single set bit followed by unset bits.