HDU 4643 GSM 暑期多校联合训练第五场 1001

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我就不说官方题解有多坑了

V图那么高端的玩意儿

被精度坑粗翔了

AC前

AC后

简直不敢相信

只能怪自己没注意题目For the distance d1 and d2, if fabs(d1-d2)<1e-7, we think d1 == d2

有空再补充V图的做法吧。。本人也是第一次接触V图

//大白p263
#include <cmath>
#include <cstdio>
#include <cstring>
#include <set>
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
const double eps=1e-8;//精度
const int INF=1<<29;
const double PI=acos(-1.0);
int dcmp(double x){//判断double等于0或。。。
    if(fabs(x)<eps)return 0;else return x<0?-1:1;
}
struct Point{
    double x,y;
    Point(double x=0,double y=0):x(x),y(y){}
};
typedef Point Vector;
typedef vector<Point> Polygon;
Vector operator+(Vector a,Vector b){return Vector(a.x+b.x,a.y+b.y);}//向量+向量=向量
Vector operator-(Point a,Point b){return Vector(a.x-b.x,a.y-b.y);}//点-点=向量
Vector operator*(Vector a,double p){return Vector(a.x*p,a.y*p);}//向量*实数=向量
Vector operator/(Vector a,double p){return Vector(a.x/p,a.y/p);}//向量/实数=向量
bool operator<( const Point& A,const Point& B ){return dcmp(A.x-B.x)<0||(dcmp(A.x-B.x)==0&&dcmp(A.y-B.y)<0);}
bool operator==(const Point&a,const Point&b){return dcmp(a.x-b.x)==0&&dcmp(a.y-b.y)==0;}
bool operator!=(const Point&a,const Point&b){return a==b;}
struct Segment{
    Point a,b;
    Segment(){}
    Segment(Point _a,Point _b){a=_a,b=_b;}
    bool friend operator<(const Segment& p,const Segment& q){return p.a<q.a||(p.a==q.a&&p.b<q.b);}
    bool friend operator==(const Segment& p,const Segment& q){return (p.a==q.a&&p.b==q.b)||(p.a==q.b&&p.b==q.a);}
};
struct Circle{
    Point c;
    double r;
    Circle(){}
    Circle(Point _c, double _r):c(_c),r(_r) {}
    Point point(double a)const{return Point(c.x+cos(a)*r,c.y+sin(a)*r);}
    bool friend operator<(const Circle& a,const Circle& b){return a.r<b.r;}
};
struct Line{
    Point p;
    Vector v;
    double ang;
    Line() {}
    Line(const Point &_p, const Vector &_v):p(_p),v(_v){ang = atan2(v.y, v.x);}
    bool operator<(const Line &L)const{return  ang < L.ang;}
};
double Dot(Vector a,Vector b){return a.x*b.x+a.y*b.y;}//|a|*|b|*cosθ 点积
double Length(Vector a){return sqrt(Dot(a,a));}//|a| 向量长度
double Angle(Vector a,Vector b){return acos(Dot(a,b)/Length(a)/Length(b));}//向量夹角θ
double Cross(Vector a,Vector b){return a.x*b.y-a.y*b.x;}//叉积 向量围成的平行四边形的面积
double Area2(Point a,Point b,Point c){return Cross(b-a,c-a);}//同上 参数为三个点
double DegreeToRadius(double deg){return deg/180*PI;}
double GetRerotateAngle(Vector a,Vector b){//向量a顺时针旋转theta度得到向量b的方向
    double tempa=Angle(a,Vector(1,0));
    if(a.y<0) tempa=2*PI-tempa;
    double tempb=Angle(b,Vector(1,0));
    if(b.y<0) tempb=2*PI-tempb;
    if((tempa-tempb)>0) return tempa-tempb;
    else return tempa-tempb+2*PI;
}
double torad(double deg){return deg/180*PI;}//角度化为弧度
Vector Rotate(Vector a,double rad){//向量逆时针旋转rad弧度
    return Vector(a.x*cos(rad)-a.y*sin(rad),a.x*sin(rad)+a.y*cos(rad));
}
Vector Normal(Vector a){//计算单位法线
    double L=Length(a);
    return Vector(-a.y/L,a.x/L);
}
Point GetLineProjection(Point p,Point a,Point b){//点在直线上的投影
    Vector v=b-a;
    return a+v*(Dot(v,p-a)/Dot(v,v));
}
Point GetLineIntersection(Point p,Vector v,Point q,Vector w){//求直线交点 有唯一交点时可用
    Vector u=p-q;
    double t=Cross(w,u)/Cross(v,w);
    return p+v*t;
}
double DistanceToSegment(Point p,Segment s){//点到线段的距离
    if(s.a==s.b) return Length(p-s.a);
    Vector v1=s.b-s.a,v2=p-s.a,v3=p-s.b;
    if(dcmp(Dot(v1,v2))<0) return Length(v2);
    else if(dcmp(Dot(v1,v3))>0) return Length(v3);
    else return fabs(Cross(v1,v2))/Length(v1);
}
bool isPointOnSegment(Point p,Segment s){//点在线段上
    return dcmp(DistanceToSegment(p,s))==0;
}
//--------------------------------------
//--------------------------------------
//--------------------------------------
//--------------------------------------
//--------------------------------------
Point city[55],bases[55];
int ans[55][55];
int sfrom[55];
Vector norm[55][55];
int n,m;
bool judge(Point p,int k){
    double dis=Length(p-bases[k]);
    for(int i=1;i<=m;i++)if(i!=k&&dcmp(dis-Length(p-bases[i])-eps)>0)
        return false;
    return true;
}
int main()
{
    while(scanf("%d%d",&n,&m)!=EOF){
        for(int i=1;i<=n;i++) scanf("%lf%lf",&city[i].x,&city[i].y);
        for(int i=1;i<=m;i++) scanf("%lf%lf",&bases[i].x,&bases[i].y);
        for(int i=1;i<=m;i++){
            for(int j=i+1;j<=m;j++){
                norm[i][j]=Normal(bases[i]-bases[j]);
            }
        }
        memset(ans,-1,sizeof ans);
        int k,star,en;
        scanf("%d",&k);
        for(int i=1;i<=n;i++){
            double temp=INF;
            int mins=-1;
            for(int j=1;j<=m;j++){
                if(dcmp(temp-Length(bases[j]-city[i]))>0){
                    temp=Length(bases[j]-city[i]);
                    mins=j;
                }
            }
            sfrom[i]=mins;
        }
        while(k--){
            scanf("%d%d",&star,&en);
            if(ans[star][en]==-1){
                ans[en][star]=ans[star][en]=0;
                Line train(city[star],city[en]-city[star]);
                for(int i=1;i<=m;i++){
                    for(int j=i+1;j<=m;j++){
                        Vector pingfenxian=norm[i][j];
                        Point midp;
                        midp.x=(bases[i].x+bases[j].x)/2;
                        midp.y=(bases[i].y+bases[j].y)/2;
                        if(dcmp(Cross(train.v,pingfenxian))==0) continue;
                        Point jiaodian=GetLineIntersection(train.p,train.v,midp,pingfenxian);
                        if(isPointOnSegment(jiaodian,Segment(city[star],city[en]))>0){
                            ans[star][en]+=judge(jiaodian,i);
                        }
                    }
                }
            }
            printf("%d\n",ans[star][en]);
            ans[en][star]=ans[star][en];
        }
    }
    return 0;
}