BZOJ 2732([HNOI2012]射箭-半平面交) (二)

#include
#include
#include
#include
#include
#include
#include
#define MAXN (100000+10)
#define MAXCi (1000000000)
#define eps 1e-15
#define For(i,n) for(int i=1;i<=n;i++)
using namespace std;
int n;
struct P
{
double x,y;
P(){}
P(double _x,double _y):x(_x),y(_y){}
}p[MAXN*4];
struct V
{
double x,y;
V(){}
V(double _x,double _y):x(_x),y(_y){}
V(P a,P b):x(b.x-a.x),y(b.y-a.y){}
friend double operator*(V a,V b){return a.x*b.y-a.y*b.x;}
friend V operator*(double a,V b){return V(a*b.x,a*b.y);}
friend P operator+(P a,V b){return P(a.x+b.x,a.y+b.y);}
};
struct line
{
P p;
V v;
double ang;
int i;
line(){}
line(double _x,double _y,double _a,double _b,int _i):p(P(_x,_y)),v(V(_a,_b)),i(_i){ang=atan2(v.y,v.x);}
bool onleft(P A)
{
return v*V(p,A)>=0;
}
bool operator<(const line& l) const
{
return ang }
friend P getinter(line a,line b)
{
/*
V u=V(a.p,b.p);
double t=(a.v*u)/(b.v*a.v);
return b.p+(t*b.v);
double s1=V(a.p,b.p+b.v)*a.v;
double s2=a.v*V(a.p,b.p);
return b.p+(-s1/(s1+s2))*b.v;
// V u=V(a.p,b.p);
*/
V u=V(b.p,a.p);
double t=(b.v*u)/(a.v*b.v);
return a.p+t*a.v;

}
}que[MAXN*10],q[MAXN*4];
int size=0;
int half_intersection(line *l,int n)
{
int first=1,last=0;
for (int i=1;i<=size;i++)
{
if (l[i].i>n) continue;
if (!last) {q[++last]=l[i];continue;}
while (first while (first if (fabs(q[last].v*l[i].v)<=eps)
{
if (q[last].onleft(l[i].p)) q[last]=l[i];
}
else q[++last]=l[i];
if (first }
bool flag=1;
while (flag)
{
flag=0;
while (first while (first }
/*
p[last]=getinter(q[last],q[first]);
for (int i=first;i<=last;i++)
printf("%lf %lf\n",p[i].x,p[i].y);
cout< */
return last-first>1;
}
void pri(line a,line b)
{
P c=getinter(a,b);
printf("%.lf %.lf\n",c.x,c.y);
}
int main()
{
freopen("archery.in","r",stdin);
freopen("archery.out","w",stdout);
cin>>n;
que[1]=line(0,0,0,1,0);
que[2]=line(-1,0,1,0,0);
que[3]=line(0,MAXCi,-1,0,0);
que[4]=line(-MAXCi,MAXCi,0,-1,0);size=4;
// pri(que[3],que[4]);
// size=0;
for (int i=1;i<=n;i++)
{
double x,l,r;
scanf("%lf%lf%lf",&x,&l,&r);
que[++size]=line(0,l/x,1/x,-1,i);
que[++size]=line(0,r/x,-1/x,1,i);
}
sort(que+1,que+1+size);
// cout< // for (int i=l;i<=r;i++) cout< // cout< int l=0,r=n,Mid=0;
while (l<=r)
{
int mid=(l+r)>>1;
if (half_intersection(que,mid)) {Mid=mid;l=mid+1;}else r=mid-1;
}
cout< return 0;
}