BZOJ 4595 SHOI2015 激光发生器 射线，线段，偏转

题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=4595

题意概述：

　　给出一条射线和N条线段，射线遇到线段会发生反射，令入射角alpha，出射角beta，则beta=alpha*phi_i（即对于每条线段phi是不同的），输出至多10条遇见的线段，没有发生相交的话输出NONE。

N<=100.

分析：

　　实际上记得板子怎么打还是没什么问题的，问题就是我当时记不得了......

　　还有一个事情，用余弦定理求两个向量夹角的时候记得-eps控制精度！

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<cstdlib>
 #include<algorithm>
 #include<cmath>
 #include<queue>
 #include<set>
 #include<map>
 #include<vector>
 #include<cctype>
 using namespace std;
 const int maxn=;
 const double eps=1e-;
 const double pi=acos(-1.0);

 int X,Y,dx,dy,N;
 struct Point{
     double x,y;
     Point(){ }
     Point(double xx,double yy){ x=xx,y=yy; }
 }P[maxn]; int cnt=;
 typedef Point Vector;
 struct Line{
     Point p; Vector v;
     Line(){    }
     Line(Point pp,Vector vv){ p=pp,v=vv; }
 };
 struct data{
     int a,b;
     Point p1,p2;
 }A[maxn];
 Vector operator + (const Vector &a,const Vector &b){ return Vector(a.x+b.x,a.y+b.y); }
 Vector operator - (const Vector &a,const Vector &b){ return Vector(a.x-b.x,a.y-b.y); }
 Vector operator * (const Vector &a,const double &b){ return Vector(a.x*b,a.y*b); }
 int dcmp(double x){ return fabs(x)<eps?:(x>?:-); }
 double Dot(const Vector &a,const Vector &b){ return a.x*b.x+a.y*b.y; }
 double Cross(const Vector &a,const Vector &b){ return a.x*b.y-a.y*b.x; }
 double Length(const Vector &a){ return sqrt(a.x*a.x+a.y*a.y); }
 double Angle(const Vector &a,const Vector &b){ return acos(fabs(Dot(a,b))/Length(a)/Length(b)-eps); }
 Vector Rotate(const Vector &v,const double &rad){
     return Vector(v.x*cos(rad)-v.y*sin(rad),v.y*cos(rad)+v.x*sin(rad));
 }
 Point GetLineIntersection(const Line &a,const Line &b){
     Vector u=a.p-b.p;
     double t=Cross(b.v,u)/Cross(a.v,b.v);
     return a.p+a.v*t;
 }
 bool Onsegment(const Point &p,const Point &a,const Point &b){
     return dcmp(Dot(a-p,b-p))<=&&dcmp(Cross(a-p,a-p))==;
 }

 void data_in()
 {
     scanf("%d%d%d%d%d",&X,&Y,&dx,&dy,&N);
     for(int i=;i<=N;i++)
         scanf("%lf%lf%lf%lf%d%d",&A[i].p1.x,&A[i].p1.y,&A[i].p2.x,&A[i].p2.y,&A[i].a,&A[i].b);
 }
 void work()
 {
     int t=;
     Point p=Point(X,Y),pp;
     Vector v=Vector(dx,dy),vv;
     while(t<=){
         double md=1e9,dis; int id=;
         for(int i=;i<=N;i++){
             if(dcmp(Cross(A[i].p1-A[i].p2,v))==) continue;
             pp=GetLineIntersection(Line(A[i].p1,A[i].p2-A[i].p1),Line(p,v));
             if(Onsegment(pp,A[i].p1,A[i].p2)&&dcmp(Dot(v,pp-p))>){
                 dis=Length(p-pp);
                 if(dis<md) md=dis,id=i;
             }
         }
         if(!id) break;
         p=GetLineIntersection(Line(A[id].p1,A[id].p2-A[id].p1),Line(p,v));
         if(dcmp(Dot(A[id].p1-A[id].p2,v))==) v=v*-;
         else{
             if(dcmp(Dot(A[id].p1-A[id].p2,v))>) vv=A[id].p1-A[id].p2;
             else vv=A[id].p2-A[id].p1;
             double alp=pi/-Angle(vv,v);
             if(dcmp(Cross(vv,v))>) v=Rotate(vv,alp*A[id].a/A[id].b-pi/);
             else v=Rotate(vv,pi/-alp*A[id].a/A[id].b);
         }
         printf("%d ",id);
         t++;
     }
     if(t==) printf("NONE\n");
 }
 int main()
 {
     data_in();
     work();
     return ;
 }