#27

Reverse the bits of an unsigned integer.


Answer:

#define reverse(x) \
(x=x>>16(0x0000ffff&x)<<16,>
x=(0xff00ff00&x)>>8(0x00ff00ff&x)<<8,>
x=(0xf0f0f0f0&x)>>4(0x0f0f0f0f&x)<<4,>
x=(0xcccccccc&x)>>2(0x33333333&x)<<2,>
x=(0xaaaaaaaa&x)>>1(0x55555555&x)<<1)