位运算基础

 

             Binary
Value        Sample             Meaning

  x         00101100        原始x的值                          the original x value
~x          11010011        按位取反
-x          11010100        按位取反再加1
a|b                         合并1
a&b                         合并0
a^b                         非进位加法，便于对某一位进行切换
x & -x      00000100        提取最末位1                         extract lowest bit set
x | -x      11111100        制造一块区域遮住最末位1及其左边区域    create mask for lowest-set-bit & bits to its left
x ^ -x      11111000        制造一块区域遮住最末位1左边的区域      create mask bits to left of lowest bit set
x & (x-1)   00101000        移除最末位1                         strip off lowest bit set
                            --> useful to process words in O(bits set)
                                instead of O(nbits in a word)
x | (x-1)   00101111        把最末尾1右边全部填为1                fill in all bits below lowest bit set
x ^ (x-1)   00000111        制造一块区域遮住最末尾的1及其右部区域   create mask for lowest-set-bit & bits to its right
~x & (x-1)  00000011        制造一块区域遮住最末尾的1右边的区域     create mask for bits to right of lowest bit set
x | (x+1)   00101101        最右边的0变1                        toggle lowest zero bit
x / (x&-x)  00001011        右移去掉所有最右边的0                 shift number right so lowest set bit is at bit 0

 

 

占位符