int numTable[256] = {
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3,
3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3,
4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4,
3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3,
4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6,
6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4,
5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 4, 5, 3,
4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 3, 4,
4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6,
7, 6, 7, 7, 8
};
//摘自《数学之美》
int numOfOne(int v)
{
int number = 0;
while(v)
{
if(v % 2 == 1)
{
number++;
}
v >>= 1;
}
return number;
}
unsigned int numOfOne2(unsigned int n)
{
unsigned int count = 0;
while(n > 0)
{
++count;
n = n & (n-1);
}
return count;
}
unsigned int hammingWeight(unsigned int n)
{
unsigned int t = n;
t = (t & 0x55555555) + ( (t & 0xAAAAAAAA) >> 1);
t = (t & 0x33333333) + ( (t & 0xCCCCCCCC) >> 2);
t = (t & 0x0f0f0f0f) + ( (t & 0xf0f0f0f0) >> 4);
t = (t & 0x00ff00ff) + ( (t & 0xff00ff00) >> 8);
t = (t & 0x0000ffff) + ( (t & 0xffff0000) >> 16);
return t;
}
void main()
{
int a = 255;
printf("%d,%d,%d,%d\n",
numTable[a],
numOfOne(a),
numOfOne2(a),
hammingWeight(a));
}
