求unsigned int i的二进制表示中1的个数

//转
int fun1(unsigned int i)
{
    if(i<2)
        return i;
    else
        return fun(i/2)+i%2;
}

int fun2(unsigned int i)
{
    int n1=0;
    while(i)
    {
        i=i&(i-1);
        n1++;
    }
    return n1;
}