BZOJ1829 : [Usaco2010 Mar]starc星际争霸

#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
const int N=400;
const double eps=1e-10;
struct P{
  double x,y;
  P(){x=y=0;}
  P(double _x,double _y){x=_x,y=_y;}
  P operator-(const P&a)const{return P(x-a.x,y-a.y);}
  P operator+(const P&a)const{return P(x+a.x,y+a.y);}
  P operator*(double a)const{return P(x*a,y*a);}
}p[N],a[N];
struct L{
  P p,v;double a;
  L(){}
  L(P _p,P _v){p=_p,v=_v;}
  bool operator<(const L&b)const{return a<b.a;}
  void cal(){a=atan2(v.y,v.x);}
}line[N],q[N];
int n,m,cl,h,t;
inline double cross(const P&a,const P&b){return a.x*b.y-a.y*b.x;}
//新的半平面，在这条向量a->b的逆时针方向
inline void newL(const P&a,const P&b){line[++cl]=L(a,b-a);}
inline bool left(const P&p,const L&l){return cross(l.v,p-l.p)>0;}
inline P pos(const L&a,const L&b){
  P x=a.p-b.p;double t=cross(b.v,x)/cross(a.v,b.v);
  return a.p+a.v*t;
}
inline void halfplane(){
  for(int i=1;i<=cl;i++)line[i].cal();
  sort(line+1,line+cl+1);
  h=t=1;
  q[1]=line[1];
  for(int i=2;i<=cl;i++){
    while(h<t&&!left(p[t-1],line[i]))t--;
    while(h<t&&!left(p[h],line[i]))h++;
    if(fabs(cross(q[t].v,line[i].v))<eps)q[t]=left(q[t].p,line[i])?q[t]:line[i];else q[++t]=line[i];
    if(h<t)p[t-1]=pos(q[t],q[t-1]);
  }
  while(h<t&&!left(p[t-1],q[h]))t--;
  p[t]=pos(q[t],q[h]);
}
int main(){
  newL(P(0,0),P(100,1));
  newL(P(100,0),P(100,100));
  newL(P(1,100),P(0,0));
  newL(P(100,100),P(0,100));
  newL(P(0.01,100),P(0.01,0));
  newL(P(0,0.01),P(100,0.01));
  scanf("%d%d",&n,&m);
  while(n--){
    char ch[5];int a,b,c,d,e,f;
    scanf("%s",ch);
    if(ch[0]==‘J‘)scanf("%d%d%d%d%d%d",&a,&b,&c,&d,&e,&f);
    else scanf("%d%d%d%d%d%d",&d,&e,&f,&a,&b,&c);
    a-=d,b-=e,c-=f;
    if(!a&&!b)continue;
    if(b){
      P A=P(0,-1.0*c/b),B=P(100,(-100.0*a-c)/b),C=A;C.y+=1;
      if(C.x*a+C.y*b+c>0)newL(A,B);else newL(B,A);
    }else{
      P A=P(-1.0*c/a,0),B=P(-1.0*c/a,100),C=A;C.x-=1;
      if(C.x*a+C.y*b+c>0)newL(A,B);else newL(B,A);
    }
  }
  halfplane();
  while(m--){
    int a,b,c,d,e,f;
    scanf("%d%d%d%d%d%d",&a,&b,&c,&d,&e,&f);
    a-=d,b-=e,c-=f;
    int flag=0;
    for(int i=h;i<=t;i++){
      double tmp=p[i].x*a+p[i].y*b+c;
      if(tmp>-eps)flag|=1;
      if(tmp<eps)flag|=2;
    }
    if(flag==1)puts("J");
    else if(flag==2)puts("B");
    else puts("U");
  }
  return 0;
}