Give a one-line C expression to test whether a number is a power of 2?

Answer 1

The one line expression is:

((0 != n) && !(n & n-1))

example:

int main ()

{

for (int n = 0; n <= 1000001; ++n)

{

if ((0 != n) && !(n & n-1))

cout << n << " is a power of 2" << endl;

}

return 0;

}

will produce:

1 is a power of 2

2 is a power of 2

4 is a power of 2

8 is a power of 2

16 is a power of 2

32 is a power of 2

64 is a power of 2

128 is a power of 2

256 is a power of 2

512 is a power of 2

1024 is a power of 2

2048 is a power of 2

4096 is a power of 2

8192 is a power of 2

16384 is a power of 2

32768 is a power of 2

65536 is a power of 2

131072 is a power of 2

262144 is a power of 2

524288 is a power of 2