首先可以把unsigned int数中的1的个数与0的个数改变与计算的实现：
</pre><pre name="code" class="cpp">/*********************************************************************** * Copyright (c)2015,WK Studios * * Filename: A.h * * Compiler: GCC vc 6.0* * Author:WK* * Time: 2015 2 7 * **********************************************************************/#include<iostream>using namespace std;#include <assert.h>void Set_Bit(size_t * Int_Dat,size_t Posi,bool ch ){if(ch){*Int_Dat |= (0x01<<(Posi-1));}else{*Int_Dat &= ~(0x01<<(Posi-1));}}size_t Cal_Bit1(size_t d){size_t n=0;while(d ){if(d & 0x01){++n;}d/=2;}return n;}size_t Cal_Bit0(size_t d){size_t n=0;while(d){if(!(d%2)) {++n;}d/=2;}return n;}size_t Cal_B1(size_t d){size_t n=0;while(d){++n;d&=(d-1);//末尾一位置0}return n;}size_t Cal_B0(size_t d){size_t n=0;while((d+1)){++n;d |= (d+1);//末尾一位置1}return n;}void main(){cout<<"—–计算无符号整型中0或者1的个数—–\n";unsigned int m=15;cout<<"原数据："<<m<<endl;cout<<"0个数："<<Cal_Bit0(m)<<endl;//这种计算忽略了前边的零cout<<"1个数："<<Cal_Bit1(m)<<endl;cout<<"0个数："<< Cal_B0(m)<<endl;//计算在32位中的零cout<<"1个数："<< Cal_B1( m)<<endl;cout<<"—–无符号整型指定位置0或者置1—–\n";unsigned int d=4;cout<<"原数据："<<d<<endl;Set_Bit( &d, 2,1 );cout<<"指定位置置1后:"<<d<<endl;Set_Bit( &d, 2,0 );cout<<"指定位置置0后:"<<d<<endl;}
用类实现在无符号整型指定的位置赋1：
#include<iostream>using namespace std;#include <assert.h>#define FSIZE 32#define TRUE 1#define FALSE 0class flags{unsigned char f[FSIZE];public:flags();void set(int i);void clear(int i );int read(int i);int size();};flags::flags(){memset(f,FALSE,FSIZE);//初始化为FSIZE位全是0}void flags::set(int i){assert(i>=0 && i<FSIZE);f[i]=TRUE;}void flags::clear(int i){assert(i>=0 && i<FSIZE);f[i]=FALSE;}int flags::read(int i){assert(i>=0 && i<FSIZE);return f[i];}int flags::size(){return FSIZE;}void main(){flags f1;for(int i=0;i<f1.size();++i){if(i%3==0)//在可以被三整除的位置赋为1f1.set(i);}for(int j=0;j<f1.size();++j){cout<<f1.read(j)<<" ";}cout<<endl;}
更加复杂的实现对无符号整型中二进制位的修改：
/********************************************************************** * * Copyright (c)2015,WK Studios * * Filename: A.h * * Compiler: GCC vc 6.0 * * Author:WK * * Time: 2015 2 7 * **********************************************************************/#include<iostream>using namespace std;#include<assert.h>#include<limits.h>const unsigned char highbit=1 << (CHAR_BIT-1);class BitVector{ public:BitVector();BitVector(unsigned char* init,int size=8);BitVector(char* Binary);//可以使用"000101010"字符串来初始化~BitVector();void set(int init);void clear(int bit);int read(int bit);void bits(int sz);int bits();void print(const char* msg="");//缺省的常量字符串仍然在常量区里保存private:unsigned char* Bytes;int Bits,NumBytes;//比特位和字节数};BitVector::BitVector()//把所有的变量赋零{NumBytes=0;Bits=0;Bytes=0;}BitVector::BitVector(unsigned char* init,int size)//分配内存并且初始化位数{NumBytes=size;//字节数11110000Bits=NumBytes*CHAR_BIT;//总共的比特位数Bytes=(unsigned char*)calloc(NumBytes,1);//void *calloc(size_t n, size_t size)；//分配NumBytes个1字节的空间assert(Bytes);if(init==NULL ){return;}for(int index=0;index<NumBytes;++index){for(int offset=0;offset<CHAR_BIT;++offset){if(init[index] & (highbit>>offset))set(index * CHAR_BIT+offset);}}}BitVector::BitVector(char* Binary){//"1111010010"assert(Binary);Bits=strlen(Binary);NumBytes=Bits/CHAR_BIT;//字节数//不足8比特位的也分配一个字节if(Bits%CHAR_BIT)NumBytes++;Bytes=(unsigned char*)calloc(NumBytes,1);assert(Bytes);for(int i=0;i<Bits;++i){if(Binary[i]=='1')set(i);}}BitVector::~BitVector(){free(Bytes);}void BitVector::set(int bit){ assert(bit>=0 && bit<Bits); int index=bit/CHAR_BIT; int offset=bit % CHAR_BIT; unsigned char mask =(1<<offset); Bytes[index] |= mask; }int BitVector::read(int bit){assert(bit>=0 && bit<Bits);int index=bit/CHAR_BIT;int offset=bit % CHAR_BIT; unsigned char mask =(1<<offset); return Bytes[index] & mask;//其实可以只用一句就结局问题，但是程序的可读性太差}void BitVector::clear(int bit){assert(bit>=0 && bit<Bits);int index=bit/CHAR_BIT;int offset=bit % CHAR_BIT;unsigned char mask =~(1<<offset);Bytes[index] &= mask; }int BitVector:: bits(){return Bits;}void BitVector::bits(int size){ int oldsize =Bits; Bits=size; NumBytes=Bits/CHAR_BIT; if(Bits%CHAR_BIT) NumBytes++; void* V=realloc(Bytes,NumBytes); assert(V); Bytes=(unsigned char*)V; for(int i=oldsize;i<Bits;++i) { clear(i); }}void BitVector::print(const char* msg){puts(msg);for(int i=0;i<Bits;i++){if(read(i))putchar('1');elseputchar('0');if((i+1)%CHAR_BIT == 0)putchar(' ');}putchar('\n');}void main(){unsigned char b[]={0x0f,0xff,0xf0,0xAA,0x78,0x11};//unsigned char b[]={'a','b','c','d','e','f'};BitVector bv1(b,sizeof (b)/sizeof (*b)),bv2("10010100111100101010001010010010101");bv1.print("bv1 before modification");for(int i=36;i<bv1.bits();++i){bv1.clear(i);}bv1.print("bv1 after modification");bv2.print("bv2 after modification");for(int j=bv2.bits()-10;j<bv2.bits();++j){bv2.clear(j);}bv2.set(30);bv2.print("bv2 after modification");bv2.bits(bv2.bits()/2);bv2.print("bv2 cut in half");bv2.bits(bv2.bits()+10);bv2.print("bv2 grown by 10");BitVector bv3((unsigned char*)0);}
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