POJ 1912 凸包

题目；

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <algorithm>
#include <set>
using namespace std;
typedef long long ll;
typedef unsigned long long Ull;
#define MM(a,b) memset(a,b,sizeof(a));
const double eps = 1e-10;
const int inf = 0x3f3f3f3f;
const double pi=acos(-1);
const int mod=100000000;

struct Point{
   double x,y;
   //Point(){};
   Point(double xx=0,double yy=0):x(xx),y(yy){}
   bool read()
    {
        return ~scanf("%lf%lf", &x, &y);
    }
   bool operator<(const Point p) const{
       if(this->x!=p.x)
         return  this->x<p.x;
       else return this->y<p.y;
   }
   double dot(Point p)
   {
       return this->x*p.x+this->y*p.y;
   }
   double getA()
   {
       double A=atan2(this->y,this->x);
       if(A<-pi/2+eps) A+=2*pi;
       return A;
   }
   Point operator-(Point p)
   {
       return Point(this->x-p.x,this->y-p.y);
   }
};

double det(Point p,Point q)
{
    return p.x*q.y-q.x*p.y;
}

int dcmp(double x)
{
    if(fabs(x)<eps) return 0;
    else if(x>0) return 1;
    else return -1;
}
Point p[100005],ans[100005];
double ang[100005];

int Convex_hull(Point *p,int n,Point *ans)
{
       sort(p+1,p+n+1);
       ans[1]=p[1];ans[2]=p[2];
       int w=2;
       for(int i=3;i<=n;i++)
       {
           int k=dcmp(det(p[i]-ans[w-1],ans[w]-ans[w-1]));
           while(dcmp(det(p[i]-ans[w-1],ans[w]-ans[w-1]))>0&&w>=2)
              w--;
           ans[++w]=p[i];
       }
       int cur=w;
       ans[++w]=p[n-1];
       for(int i=n-2;i>=2;i--)
       {
           int k=dcmp(det(p[i]-ans[w-1],ans[w]-ans[w-1]));
           while(dcmp(det(p[i]-ans[w-1],ans[w]-ans[w-1]))>0&&w>=cur+1)
             w--;
           ans[++w]=p[i];
       }
       return w;
}

int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        for(int i=1;i<=n;i++) p[i].read();
        int m=0;
        if(n>1) {m=Convex_hull(p,n,ans);}
        ans[m+1]=ans[0];
        for(int i=1;i<=m;i++)
            ang[i]=(ans[i+1]-ans[i]).getA();
        Point q[3];
        while(q[1].read())
        {
            q[2].read();
            int i=upper_bound(ang+1,ang+m+1,(q[2]-q[1]).getA())-ang;
            int j=upper_bound(ang+1,ang+m+1,(q[1]-q[2]).getA())-ang;
            if(n>1&&dcmp(det(q[2]-q[1],ans[i]-q[1]))*dcmp(det(q[2]-q[1],ans[j]-q[1]))<0)
               printf("BAD\n");
            else printf("GOOD\n");
        }
    }
    return 0;
}