poj 2187

典型的旋转卡壳，有两种方法：

  一：先求凸包，然后一一枚举凸包上的每两个点

  二：裸的旋转卡壳。

 顺便推荐一个讲旋转卡壳的好地方~  http://www.cnblogs.com/Booble/archive/2011/04/03/2004865.html

//凸包 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
const int MAX = 120000;
const double eps = 1e-6;
const double pi=3.141592654;
bool dy(double x,double y)	{	return x > y + eps;}	// x > y 
bool xy(double x,double y)	{	return x < y - eps;}	// x < y 
bool dyd(double x,double y)	{ 	return x > y - eps;}	// x >= y 
bool xyd(double x,double y)	{	return x < y + eps;} 	// x <= y 
bool dd(double x,double y) 	{	return fabs( x - y ) < eps;}  // x == y
struct point{	double x,y;		};
point c[MAX];
double disp2p(point a,point b) 
{
	return  ( a.x - b.x ) * ( a.x - b.x ) + ( a.y - b.y ) * ( a.y - b.y );
}
double crossProduct(point a,point b,point c)//向量 ac 在 ab 的方向 
{
	return (c.x - a.x)*(b.y - a.y) - (b.x - a.x)*(c.y - a.y);
}
bool cmp(point a,point b)  // 排序   
{  
    double len = crossProduct(c[0],a,b);  
    if( dd(len,0.0) )  
        return xy(disp2p(c[0],a),disp2p(c[0],b));  
    return xy(len,0.0);  
}  
int stk[MAX];
int top;	
double sum = 0.0;
void Graham(int n)
{
    int tmp = 0;  
    for(int i=1; i= 1 )
			top--;
		stk[++top] = i;
	}
	//cout<<"top "<>n&& n )
	{
		  for(int i=0;i>c[i].x>>c[i].y;
          Graham(n);
          double nowlen;
          len=0.0;
        for(int i=0; i<=top; i++)
		  for(int j=0;j<=top;j++)
            if(j!=i)
            {
             nowlen=disp2p(c[stk[i]],c[stk[j]]);
             if(nowlen>len) len=nowlen;
            }
            /*
            想不明白，凸包上不相邻两点的 距离肯定大于相邻两点，但是 WA 。如果一一枚举凸包上点 ，A 。 
            for(int i=0; ilen) len=nowlen;
            }
            */
            
         printf("%.0lf\n",len);
	}
return 0;
}

//卡壳 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
const int MAX = 120000;
const double eps = 1e-6;
const double pi=3.141592654;
bool dy(double x,double y)	{	return x > y + eps;}	// x > y 
bool xy(double x,double y)	{	return x < y - eps;}	// x < y 
bool dyd(double x,double y)	{ 	return x > y - eps;}	// x >= y 
bool xyd(double x,double y)	{	return x < y + eps;} 	// x <= y 
bool dd(double x,double y) 	{	return fabs( x - y ) < eps;}  // x == y
struct point{	double x,y;		};
point c[MAX];
double disp2p(point a,point b) 
{
	return  ( a.x - b.x ) * ( a.x - b.x ) + ( a.y - b.y ) * ( a.y - b.y );
}
double crossProduct(point a,point b,point c)//向量 ac 在 ab 的方向 
{
	return (c.x - a.x)*(b.y - a.y) - (b.x - a.x)*(c.y - a.y);
}
bool cmp(point a,point b)  // 排序   
{  
    double len = crossProduct(c[0],a,b);  
    if( dd(len,0.0) )  
        return xy(disp2p(c[0],a),disp2p(c[0],b));  
    return xy(len,0.0);  
}  
int stk[MAX];
int top;	
double sum = 0.0;
void Graham(int n)
{
    int tmp = 0;  
    for(int i=1; i= 1 )
			top--;
		stk[++top] = i;
	} 
	//cout<<"top "<>n&& n )
	{
		  for(int i=0;i>c[i].x>>c[i].y;
          Graham(n);          
          len=Rotating_calipers(stk,top+1);  //注意：是 top+1     
        printf("%.0lf\n",len);
	}
return 0;
}