hdu4998 Rotate 计算几何

Noting is more interesting than rotation!

Your little sister likes to rotate things. To put it easier to analyze, your sister makes n rotations. In the i-th time, she makes everything in the plane rotate counter-clockwisely around a point ai by a radian of pi.

Now she promises that the total effect of her rotations is a single rotation around a point A by radian P (this means the sum of pi is not a multiplier of 2π).

Of course, you should be able to figure out what is A and P :).

计算几何

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<cmath>
 using namespace std;
 const double eps=1e-;
 const double pi=acos(-1.0);

 int sgn(double x){
     if(fabs(x)<eps) return ;
     if(x<) return -;
     else return ;
 }

 struct Point{
     double x,y;
     Point(){}
     Point(double _x,double _y){
         x=_x;
         y=_y;
     }
     Point operator -(const Point &b)const{
         return Point(x-b.x,y-b.y);
     }
     double operator ^(const Point &b)const{
         return x*b.y-y*b.x;
     }
     double operator *(const Point &b)const{
         return x*b.x+y*b.y;
     }
     Point operator +(const Point &b)const{
         return Point(x+b.x,y+b.y);
     }
     Point operator *(const double &k)const{
         return Point(x*k,y*k);
     }
     Point operator /(const double &k)const{
         return Point(x/k,y/k);
     }
     Point rotate(Point p,double angle){
         Point v=(*this)-p;
         double c=cos(angle),s=sin(angle);
         return Point(p.x+v.x*c-v.y*s,p.y+v.x*s+v.y*c);
     }
     double len2(){
         return x*x+y*y;
     }
 };

 struct Line{
     Point s,e;
     Line(){}
     Line(Point _s,Point _e){
         s=_s;
         e=_e;
     }
     Point crosspoint(Line v){
         double a1=(v.e-v.s)^(s-v.s);
         double a2=(v.e-v.s)^(e-v.s);
         return Point((s.x*a2-e.x*a1)/(a2-a1),(s.y*a2-e.y*a1)/(a2-a1));
     }
     Point lineprog(Point p){
         return s+( ((e-s)*((e-s)*(p-s)))/((e-s).len2()) );
     }
 };

 void solve(){
     int n,i;
     double x,y,p,nx,ny,np;
     Point a,b,c,d,e,f,g;
     Line l1,l2,l3,l4;
     scanf("%d",&n);
     scanf("%lf%lf%lf",&nx,&ny,&np);
     for(i=;i<=n;i++){
         scanf("%lf%lf%lf",&x,&y,&p);
         a=Point(nx,ny);b=Point(x,y);
         d=a.rotate(b,p);c=b.rotate(a,-np);
         l1=Line(c,b);l2=Line(a,d);
         e=l1.lineprog(a);f=l2.lineprog(b);
         l3=Line(a,e);l4=Line(b,f);
         g=l3.crosspoint(l4);
         nx=g.x;ny=g.y;
         np=np+p;
         if(np>*pi) np-=*pi;
     }
     printf("%lf %lf %lf\n",nx,ny,np);
 }

 int main(){
     int t;
     scanf("%d",&t);
     while(t)solve();
     return ;
 }