bzoj 4595 激光发生器

bzoj 4595 激光发生器

• 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<bits/stdc++.h>
using namespace std;
#define ll long long
#define mp make_pair
#define pii pair<int,int>
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 v2
v2 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<mdis)
										mdis=dis,id=i;
								}
						}
				}
			if(id==0)
				break;
			++cnt;
			p=inter(a[id].p1,a[id].p2-a[id].p1,p,v);
			if(dcmp(dot(a[id].p1-a[id].p2,v)==0))
				v=v2(-v.x,-v.y);
			else
				{
					vector t=a[id].p2-a[id].p1;
					if(dcmp(dot(a[id].p1-a[id].p2,v)>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;
}