Answer / dan

if (x & (x-1)) // false only if x is a power of 2

Answer / vadivel

# include <stdio.h>

void main()
{
int n;
scanf("%d",&n);
if( n & (n-1) )
printf("Not a Power of 2");
else
printf("Power of 2");
}

Answer / ataraxic

Previous post -- It's wrong... absolutely...

Answer / phil

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

Answer / jb

(x ^ x-1) == ((x << 1) - 1)

Answer / ashutosh

I think
if (x & (x-1)) wont work when number is negative.

Answer / natmat

(~i & (i-1)) == (i - 1))

Answer / fjords

if (int(log(x)) == log(x)) // log is to the base 2

Answer / rahul priyadarshi

#define ISPOW2(x) ((x==1)?1:(x&(x-1)))?0:1

Answer / yevgen

if ((num XOR (num - 1)) == num + num - 1) return true;
else return false;

Give a oneline C expression to test whether a number is a power of 2?

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