三種方法計(jì)算二進(jìn)制中1的個(gè)數(shù)，最后一種比較炸裂！

#include 


int main()
{
    int x = 1000, count = 0;


    for (int i = 0; i < 32; i++)
    {   
        if (x & 0x01)
        {   
            count++;
        }   


        x = x >> 1;
    }   


    printf("%d
", count);


return 0;
}

#include 


int main()
{
    int x = 1000, count = 0;


    while (x) 
    {   
        x = x & (x - 1); 
        count++;
    }   


    printf("%d
", count);
    return 0;
}

#include 


int main()
{ 
    unsigned int temp = 1000; 


    temp = (temp & 0x55555555) + ((temp & 0xaaaaaaaa)>>1);
    temp = (temp & 0x33333333) + ((temp & 0xcccccccc)>>2);
    temp = (temp & 0x0f0f0f0f) + ((temp & 0xf0f0f0f0)>>4);
    temp = (temp & 0xff00ff) + ((temp & 0xff00ff00)>>8);
    temp = (temp & 0xffff) + ((temp & 0xffff0000)>>16);


    printf("%d
", temp);


    return 0;  
}

0001 0001100100110000100000101000

temp = (temp & 0x55555555) + ((temp & 0xaaaaaaaa)>>1);
temp=(temp&0x33333333)+((temp&0xcccccccc)>>2);
temp=(temp&0x0f0f0f0f)+((temp&0xf0f0f0f0)>>4);
temp=(temp&0xff00ff)+((temp&0xff00ff00)>>8);
temp=(temp&0xffff)+((temp&0xffff0000)>>16);

0001 0001 1001 0011 0000 1000 0010 1000

0 1 0 1 1 1 0 2 0 0 1 0 0 1 1 0

0001000101010010 0000 0100 0001 010

1 1 2 2 0 1 1 1

0001 0001 0010 0010 0000 0001 0001 0001

2 4 1 2

0000001000000100 0000 0001 0000 0010

6 3

0000 0000 0000 0110 0000 0000 0000 0011

9

00000000000000000000000000001001