计算几何_二维几何模板

#include<iostream>
#include<cmath>

const double eps=1e-10;


using namespace std;


struct Point{
    double x;
    double y;
    Point(double x=0,double y=0):x(x),y(y){}
   
};

int dcmp(double x)  {return x>eps-x<-eps; }

typedef  Point  Vector;
    
  Vector  operator +(Vector A,Vector B) { return Vector(A.x+B.x,A.y+B.y);}

  Vector  operator -(Vector A,Vector B) { return Vector(A.x-B.x,A.y-B.y); }

  Vector  operator *(Vector A,double p) { return Vector(A.x*p,A.y*p);  }

  Vector  operator /(Vector A,double p) {return Vector(A.x/p,A.y/p);}

  bool  operator< (Vector A,Vector B) { return A.x<B.x||(A.x==B.x&&A.y<B.y); }

  bool  operator== (Vector A,Vector B) { return dcmp(A.x-B.x)==0&&dcmp(A.y-B.y);}


double  Dot(Vector A,Vector B) {return A.x*B.x+A.y*B.y;}

double  Cross(Vector A,Vector B)  {return A.x*B.y-B.x*A.y; }

double  Length(Vector A)  { return sqrt(Dot(A, A));}


double  Angle(Vector A,Vector B) {return acos(Dot(A,B)/Length(A)/Length(B));}

double  Area2(Point A,Point B,Point C ) {return Cross(B-A, C-A);}

Vector Rotate(Vector A,double rad) { return Vector(A.x*cos(rad)-A.y*sin(rad),A.x*sin(rad)+A.y*cos(rad));}

Point GetLineIntersection(Point P,Vector v,Point Q,Vector w)
{
    Vector u=P-Q;
    double t=Cross(w, u)/Cross(v,w);
    return P+v*t;
    
}

double DistanceToLine(Point P,Point A,Point B)
{
    Vector v1=P-A; Vector v2=B-A;
    return fabs(Cross(v1,v2))/Length(v2);
    
}

double DistanceToSegment(Point P,Point A,Point B)
{
    if(A==B)  return Length(P-A);
    
    Vector v1=B-A;
    Vector v2=P-A;
    Vector v3=P-B;
    
    if(dcmp(Dot(v1,v2))==-1)    return  Length(v2);
    else if(Dot(v1,v3)>0)    return Length(v3);
    
    else return DistanceToLine(P, A, B);
    
}

 Point GetLineProjection(Point P,Point A,Point B)
{
    Vector v=B-A;
    Vector v1=P-A;
    double t=Dot(v,v1)/Dot(v,v);
    
    return  A+v*t;
}

bool  SegmentProperIntersection(Point a1,Point a2,Point b1,Point b2)
{
    double c1=Cross(b1-a1, a2-a1);
    double c2=Cross(b2-a1, a2-a1);
    double c3=Cross(a1-b1, b2-b1);
    double c4=Cross(a2-b1, b2-b1);
   
    return dcmp(c1)*dcmp(c2)<0&&dcmp(c3)*dcmp(c4)<0 ;

}

bool  OnSegment(Point P,Point A,Point B)
{
    return dcmp(Cross(P-A, P-B))==0&&dcmp(Dot(P-A,P-B))<0;
}

double PolygonArea(Point *p,int n)
{
    double area=0;
    
    for(int i=1;i<n-1;i++)
    {
        area+=Cross(p[i]-p[0], p[i+1]-p[0]);
        
    }
    return area/2;
    
}

int main()
{
    
}