Shape of HDU HDU - 2108 凸包

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

const int maxn=1000;
const double eps=1e-8;


struct Point
{
    double x,y;
    Point(){}
    Point(double _x,double _y)
    {
        x=_x;
        y=_y;
    }
    Point operator -(const Point &b)const
    {
        return Point(x-b.x,y-b.y);
    }
    double operator ^(const Point &b)const
    {
        return x*b.y-y*b.x;
    }
    double operator *(const Point &b)const
    {
        return x*b.x+y*b.y;
    }
};

Point p[maxn];
int Stack[maxn];
int top=0;


double dist(Point a,Point b)
{
    return sqrt((a-b)*(a-b));
}
bool cmp(Point a,Point b)
{
    double t=((a-p[0])^(b-p[0]));
    if(t>0)
        return true;
    else if(t==0)
        return dist(a,p[0])>n;
        if(n==0)
            break;
        if(n<=2)
        {
            printf("concave\n");
        }
        else
        {
            for(int i=0;i>p[i].x>>p[i].y;
        }
        if(gram(n)==1)
            printf("convex\n");
        else
            printf("concave\n");
        }

    }
    return 0;
}