Will you solve this tricky question?

[RAJJUMOTE]

how would you decide a number is some power of 2 in c? no loops are allowed and this should be done in one statement.

[laitinen]

bool IsPowerOfTwo (int number)
{
return number ? ((number & -number)==number):false;
}

Laitinen

[jim enright]

double SomeNumber, SomeExponent;

SomeNumber = 2**SomeExponent;
log(SomeNumber) = SomeExponent * log(2);
SomeExponent = log(SomeNumber) / log(2);

is SomeExponent an integer?

in theory:

if SomeExponent - floor(SomeExponent) = 0;

in practice:

double epsilon;
epsilon = .00001;
if abs( SomeExponent - floor(SomeExponent) ) < epsilon;

[S_M_A]

Pretty cool solution Latinen.

[Graham]

Folks, we should be determining that this is not a homework question, or that the OP has at least attempted it, before answering. The form of the OP certainly suggests that it is.

[Graham]

Pretty cool solution Latinen.

For integers, there's an even simpler solution.

(ETA: I suppose I should say conceptually simpler...)

[sandodo]

let me remove my codes.

[Paul McKenzie]

how would you decide a number is some power of 2 in c? no loops are allowed and this should be done in one statement.

Note that it's always the person with only 1 or 2 posts that asks these kind of questions.

Definitely a homework question, since the OP has not appeared since he now has something to take back to the teacher. We should be much better sniffing out "do my homework" posts, and not provide answers.

Regards,

Paul McKenzie

[TheCPUWizard]

Note that it's always the person with only 1 or 2 posts that asks these kind of questions.

Definitely a homework question, since the OP has not appeared since he now has something to take back to the teacher. We should be much better sniffing out "do my homework" posts, and not provide answers.

Regards,

Paul McKenzie

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