• 光线为射线,每次找到与当前光线相交且距离最近的镜子,然后旋转光线.
• 直线,射线利用线上一点+方向向量的方式表示.旋转时,旋转中心作为线上一点不变,方向向量左乘旋转矩阵.
• 即逆时针转过 \(\theta\) 角,方向向量 \((x,y)\) 变为 \((cos\theta \cdot x-sin\theta \cdot y,sin\theta\cdot x+cos\theta\cdot y)\).
• 实现时特判较多,需注意细节.

#include
    
     using namespace std;#define ll long long#define mp make_pair#define pii pair
     
      inline int read(){    int x=0;    bool pos=1;    char ch=getchar();    for(;!isdigit(ch);ch=getchar())        if(ch=='-')            pos=0;    for(;isdigit(ch);ch=getchar())        x=x*10+ch-'0';    return pos?x:-x;}const int MAXN=110;const double eps=1e-8;int dcmp(double x){    return fabs(x)<=eps?0:(x>0?1:-1);}struct v2{    double x,y;    v2(double x=0,double y=0):x(x),y(y) {}    v2 operator + (const v2 &rhs) const        {            return v2(x+rhs.x,y+rhs.y);        }    v2 operator / (const double &rhs) const        {            return v2(x/rhs,y/rhs);        }    v2 operator - (const v2 &rhs) const        {            return v2(x-rhs.x,y-rhs.y);        }    double operator * (const v2 &rhs) const        {            return x*rhs.y-y*rhs.x;        }    double modulus()        {            return sqrt(x*x+y*y);        }};#define point v2#define vector v2v2 rotate(v2 v,double rad){    return v2(v.x*cos(rad)-v.y*sin(rad),v.x*sin(rad)+v.y*cos(rad));}v2 inter(point p,vector v,point q,vector w){    v2 u=p-q;    double t=(w*u)/(v*w);    return p+v2(v.x*t,v.y*t);}double dot(v2 a,v2 b){    return a.x*b.x+a.y*b.y;}bool onseg(point p,point a1,point a2){    return dcmp((a1-p)*(a2-p))==0 && dcmp(dot(a1-p,a2-p))<0; }double angle(v2 a,v2 b){    return acos(fabs(dot(a,b)/a.modulus()/b.modulus()-eps));}struct mir{    v2 p1,p2;    double a,b;}a[MAXN];double x,y,dx,dy;int n;int main(){    int cnt=0;    scanf("%lf%lf%lf%lf",&x,&y,&dx,&dy);    n=read();    for(int i=1;i<=n;++i)        scanf("%lf%lf%lf%lf%lf%lf",&a[i].p1.x,&a[i].p1.y,&a[i].p2.x,&a[i].p2.y,&a[i].a,&a[i].b);    point p(x,y);    vector v(dx,dy);    for(int T=1;T<=10;++T)        {            double mdis=1e100;            int id=0;            for(int i=1;i<=n;++i)                {                    if(dcmp((a[i].p1-a[i].p2)*v)!=0)                        {                            point t=inter(a[i].p1,a[i].p2-a[i].p1,p,v);                            if(onseg(t,a[i].p1,a[i].p2) && dcmp(dot(v,t-p))>0)                                {                                    double dis=(p-t).modulus();                                    if(dis
      
       0))                        t=t/(-1);                    double alpha=acos(-1)/2-angle(t,v);                    int bt=dcmp(t*v);                    v=rotate(t,bt*(alpha*a[id].a/a[id].b-acos(-1)/2));                }            printf("%d ",id);        }    if(!cnt)        puts("NONE");    return 0;}