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c语言的位操作
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一、基本位操作
| | 或 |
& | 与 |
~ | 取反 |
^ | 异或 |
<< | 左移 |
>> | 右移 |
二、位操作的常见用法
1.获取某位的值
1 2 3 4 | #define BitGet(Number,pos) ((Number)|= 1<<(pos)) //把某位置1 #define BitGet(Number,pos) ((Number) &= ~(1<<(pos)) //把某位置0 #define BitGet(Number,pos) ((Number) >> (pos)&1)) //用宏得到某数的某位 #define BitGet(Number,pos) ((Number) ^= 1<<(pos)) //把Number的POS位取反 |
2.设定某位的值(设为0或1)
方法一:
1 2 | #define setbit(x,y) x|=(1<<y) //将x的第y位置1 #define clrbit(x,y) x&=~(1<<y) //将x的第y位清0 |
方法二:
1 2 3 4 5 6 7 8 | 置0,用0去‘与’ int a|=(1<<x) x就是某位需要置1的数字,如第四位置1为:int a |= (1<<4) 置1,用1去‘或’ int a&=~(1<<x) 把某位置0 |
3.循环移位
1 2 | #define ROTATE_LEFT(x, n) ((x) << (n)) | ((x) >> ((8 * sizeof(x)) - (n))) #define ROTATE_RIGHT(x, n) ((x) >> (n)) | ((x) << ((8 * sizeof(x)) – (n))) |
4.计算绝对值
1 2 3 4 5 | int abs(int x){ int y; y = x>>31; return (x^y)-y; //or:(x+y)^y } |
5.判断整数的符号
1 2 3 | int sign(int x){ return (x>>31)|(unsigned(-x))>>31; } |
6.两个数比较
1 2 3 4 5 6 | x==y: ~(x-y|y-x) x!=y: x-y|y-x x<y: (x-y)^((x^y)&((x-y)^x)) x<=y: (x|~y)&((x^y)|~(y-x)) x<y: (~x&y)|((~x|y)&(x-y))//无符号x,y比较 x<=y: (~x|y)&((x^y)|~(y-x))//无符号x,y比较 |
7.交换两个数的值(swap)
1 2 3 4 | 1.x ^= y ; y ^= x ; x ^= y ; 2.x = x+y ; y = x-y ; x = x-y ; 3.x = x-y ; y = y+x ; x = y-x ; 4.x = y-x ; x = y-x ; x = x+y ; |
8.位计数
方法一:
1 2 3 4 5 6 7 8 | int count(long v){ int number = 0; while(v){ v &= (v-1); number++; } return number; } |
方法二:
1 2 3 4 5 6 7 8 | int count(unsigned x){ x = x-((x>>1)&0x55555555) ; x = (x&0x33333333)+(x>>2)&0x33333333); x = (x+(x>>4))&0x0f0f0f0f; x = x+(x>>8); x = x+(x>>16); return x&0x0000003f; } |
9.二进制和GRAY码的转换
(1).二进制码到GRAY码的转换:
1 2 3 | unsigned B2G(unsigned B ){ return B ^ (B>>1) ; } |
(2).GRAY码到二进制码:
1 2 3 4 5 6 7 8 9 | unsigned G2B(unsigned G){ unsigned B ; B = G ^ (G>>1) ; B = G ^ (G>>2) ; B = G ^ (G>>4) ; B = G ^ (G>>8) ; B = G ^ (G>>16) ; return B ; } |
10.位反转
1 2 3 4 5 6 7 | unsigned rev(unsigned x){ x = (x & 0x55555555) << 1 | (x>>1) & 0x55555555 ; x = (x & 0x33333333) << 2 | (x>>2) & 0x33333333 ; x = (x & 0x0f0f0f0f) << 4 | (x>>4) & 0x0f0f0f0f ; x = (x<<24) | ((x&0xff00)<<8) | ((x>>8) & 0xff00) | (x>>24) ; return x ; } |
转载自胡超博客:http://imhuchao.com/423.html
c语言的位操作