数が2のべき乗であるかどうかをテストします.

#include <iostream>
using namespace std;


bool TestPower(int n)
{
    if (n == 1)
        return false;
    int count = 0;
    do 
    {
        if (n & 1 == 1)
        {
            ++count;
            if (count > 1)
                return false;
        }
    } while ( (n >>= 1) > 0);

    if (count == 1)
        return true;
    else
        return false;
}


int main()
{
    int a = 4;
    int b = 1024;
    int c = 1023;

    if (TestPower(a))
        cout<<"a is power of 2"<<endl;
    else
        cout<<"a is not power of 2"<<endl;

    if (TestPower(b))
        cout<<"b is power of 2"<<endl;
    else
        cout<<"b is not power of 2"<<endl;

    if (TestPower(c))
        cout<<"c is power of 2"<<endl;
    else
        cout<<"c is not power of 2"<<endl;

    return 0;
}