Answer by jerrymouse for How to check if a number is a power of 2

A number is a power of 2 if it contains only 1 set bit. We can use this property and the generic function countSetBits to find if a number is power of 2 or not.

This is a C++ program:

int countSetBits(int n){        int c = 0;        while(n)        {                c += 1;                n  = n & (n-1);        }        return c;}bool isPowerOfTwo(int n){                return (countSetBits(n)==1);}int main(){    int i, val[] = {0,1,2,3,4,5,15,16,22,32,38,64,70};    for(i=0; i<sizeof(val)/sizeof(val[0]); i++)        printf("Num:%d\tSet Bits:%d\t is power of two: %d\n",val[i], countSetBits(val[i]), isPowerOfTwo(val[i]));    return 0;}

We dont need to check explicitly for 0 being a Power of 2, as it returns False for 0 as well.

OUTPUT

Num:0   Set Bits:0   is power of two: 0Num:1   Set Bits:1   is power of two: 1Num:2   Set Bits:1   is power of two: 1Num:3   Set Bits:2   is power of two: 0Num:4   Set Bits:1   is power of two: 1Num:5   Set Bits:2   is power of two: 0Num:15  Set Bits:4   is power of two: 0Num:16  Set Bits:1   is power of two: 1Num:22  Set Bits:3   is power of two: 0Num:32  Set Bits:1   is power of two: 1Num:38  Set Bits:3   is power of two: 0Num:64  Set Bits:1   is power of two: 1Num:70  Set Bits:3   is power of two: 0