poj 2187 Beauty Contest

凸包旋转卡壳

#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

#define N 50010
#define epx 1e-8

inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch<='9'&&ch>='0'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

int n,m,top;
double Ans;
struct Point{
    double x,y;
    Point operator - (const Point &a) const{
        Point tmp;
        tmp.x=x-a.x,tmp.y=y-a.y;
        return tmp;
    }
    double operator * (const Point &a) const{
        return x*a.y-y*a.x;
    }
}p[N],S[N];

double Dis(Point a,Point b)
{
    return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
}

bool Cmp(const Point &a,const Point &b)
{
    if(fabs((b-p[1])*(a-p[1]))0;
}

void Graham()
{
    int t=1;
    for(int i=2;i<=n;i++)
        if(p[i].y1)
            top--;
        S[++top]=p[i];
    }
}

void RC()
{
    S[top+1]=p[1];
    int now=2;
    for(int i=1;i<=top;i++)
    {
        while((S[i+1]-S[i])*(S[now]-S[i])<(S[i+1]-S[i])*(S[now+1]-S[i]))
        {
            now++;
            if(now==top+1)now=1;
        }
        Ans=max(Ans,max(Dis(S[now],S[i+1]),Dis(S[now],S[i])));
    }
}

int main()
{
    n=read();
    for(int i=1;i<=n;i++)
        p[i].x=read(),p[i].y=read();
    Graham();RC();
    printf("%lld\n",(long long)Ans);
    return 0;
}