计算几何初步（刷蓝书）

#include<bits/stdc++.h>
#define max(a,b) (a>b?a:b)
#define min(a,b) (a<b?a:b)
using namespace std;
typedef long long ll;
const int maxn = 1e3+7;
const double esp = 1e-6;
int dcmp(double x){
    if(fabs(x)<esp)return 0;
    return x<0?-1:1;
}
struct Point{
    double x,y;
    void read(){scanf("%lf%lf",&x,&y);}
    Point(double x = 0,double y = 0):x(x),y(y){}
};
double Cross(const Point A,const Point B){ return A.x*B.y-A.y*B.x; }
double Dot(const Point A,const Point B){ return A.x*B.x+A.y*B.y; }
double Len(const Point A){ return sqrt(Dot(A,A)); }
double Angle(const Point A,const Point B){ return acos(Dot(A,B)/Len(A)/Len(B)); }
Point operator + (const Point A,const Point B){ return Point(A.x+B.x,A.y+B.y); }
Point operator - (const Point A,const Point B){ return Point(A.x-B.x,A.y-B.y); }
Point operator * (const Point A,const double B){ return Point(A.x*B,A.y*B); }
Point operator / (const Point A,const double B){ return Point(A.x/B,A.y/B); }
Point Rotate(const Point A,double rad){return Point(A.x*cos(rad)-A.y*sin(rad),A.x*sin(rad)+A.y*cos(rad));}
//负数表示顺时针
Point Normal(const Point A){return Point(-A.y/Len(A),A.x/Len(A));}//法向量
bool operator == (const Point A,const Point B){return !dcmp(A.x-B.x)&&!dcmp(A.y-B.y); }
bool operator != (const Point A,const Point B){return !(A == B);}
bool operator < (const Point A,const Point B){return A.x<B.x || (A.x == B.x&&A.y<B.y);}
typedef Point Vector;
struct Circle{
    Point x;
    double r;
    void read(){
        x.read();
        scanf("%lf",&r);
    }
};
bool quickRepel(Point x1,Point y1,Point x2,Point y2){//快速排斥
    Point Lx = Point(min(x1.x,y1.x),min(x1.y,y1.y));
    Point Rx = Point(max(x1.x,y1.x),max(x1.y,y1.y));

    Point Ly = Point(min(x2.x,y2.x),min(x2.y,y2.y));
    Point Ry = Point(max(x2.x,y2.x),max(x2.y,y2.y));

    Point L = Point(max(Lx.x,Ly.x),max(Lx.y,Ly.y));
    Point R = Point(min(Rx.x,Ry.x),min(Rx.y,Ry.y));

    return (L.x<=R.x) && (L.y<=R.y);
}
bool OnSegment(Point P,Point x,Point y){//点在线段上
    if(P == x||P == y)return 1;
    return !dcmp(Cross(x-P,y-P))&&dcmp(Dot(P-x,P-y))<0;
}
bool straddle(Point x1,Point y1,Point x2,Point y2){//跨立实验(线段是否有交点)
    if(!quickRepel(x1,y1,x2,y2))return 0;
    double c1 = Cross(y1-x1,x2-x1),c2 = Cross(y1-x1,y2-x1);
    double c3 = Cross(y2-x2,x1-x2),c4 = Cross(y2-x2,y1-x2);
    return dcmp(c1)*dcmp(c2)<=0 && dcmp(c3)*dcmp(c4)<=0;
    //允许部分重合或在端点重合
    //return dcmp(c1)*dcmp(c2)<0 && dcmp(c3)*dcmp(c4)<0;
    //必须只有一个交点且不在端点上
}
Point LinearIntersection(Point P,Vector v,Point Q,Vector w){//解直线交点
    assert(v != w);//Parallel 平行线
    Vector u = P-Q;
    double t = Cross(w,u)/Cross(v,w);
    return P+v*t;
}
Point GetLineProjection(Point P,Point A,Point B){//P投影到AB上的点
    Vector v = B-A;
    return A+v*(Dot(v,P-A)/Dot(v,v));
}
Point SymmetricPoint(Point P,Point A,Point B){//P关于AB的对称点
    return GetLineProjection(P,A,B)*2.0-P;
}
double DistanceToline(Point P,Point A,Point B){//点到直线距离
    Vector v1 = B-A,v2 = P-A;
    return fabs(Cross(v1,v2))/Len(v1);
}
double DistanceToSegment(Point P,Point A,Point B){//点到线段距离
    if(A == B)return Len(P-A);
    Vector v1 = B-A,v2 = P-A,v3 = P-B;
    if(dcmp(Dot(v1,v2))<0)return Len(v2);
    if(dcmp(Dot(v1,v3))>0)return Len(v3);
    return fabs(Cross(v1,v2))/Len(v1);
}