取整数绝对值的宏定义

#include <iostream>
#include <assert.h>
#include <algorithm>
#include <hash_set>
#include <vector>
#include <string>
#include <assert.h>
#include <list>
using namespace std;
#define abss(x) ((  1-((((x)>>(sizeof(x)*8-1))&1)<<1))*(x))
int main()
{
	int a=-9;
	int b=8;
	int c=0;
	int d=-100;
	cout<<"int: "<<endl;
	cout<<a<<" "<<abss(a)<<endl;
	cout<<b<<" "<<abss(b)<<endl;
	cout<<c<<" "<<abss(c)<<endl;
	cout<<d<<" "<<abss(d)<<endl;
	long long xx=-1999;
	cout<<endl<<"long long "<<endl<<xx<<" "<<abss(xx)<<endl;
	char ch=a+128;
	cout<<endl<<"char "<<endl<<ch<<" "<<abss(ch)<<endl;

	return 0;
}

 

1.为了兼容各种宽度的整数，采用sizeof

2.为了兼容右移操作时，左边补0还是补符号位的不同，右移之后与1做与操作

 

BITMAP的一个实现：

class BitMap
{
public:
 static const int N=1000;
 BitMap(){memset(an,0,N*4);}
 void SetBit(int x)
 {
  an[(x>>5)] |= (1<<(x%32));
 }
 void ClearBit(int x)
 {
  an[(x>>5)] &= ~(1<<(x%32));
 }
 int GetBit(int x)
 {
  return (an[x>>5] >> (x%32))&1; 
 }
private:
 int an[N];
};