POJ 1375 Intervals | 解析几何

参考了这个博客

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
using namespace std;
struct point
{
double x,y;
point(){};
point(double _x,double _y)
{
x=_x,y=_y;
}
}p,q;
struct range
{
double l,r;
bool operator <(const range &a) const
{
return l<a.l;
}
}line[505];
double dist(point a,point b)
{
return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
double r;
int n,t;
int main()
{
while (scanf("%d",&n)!=EOF && n)
{
scanf("%lf%lf",&p.x,&p.y);
for (int i=1;i<=n;i++)
{
scanf("%lf%lf%lf",&q.x,&q.y,&r);
double d=dist(p,q);
double a=asin(r/d),b=asin((p.x-q.x)/d);
// printf("a:%lf b:%lf\n",a,b);
line[i].r=p.x-p.y*tan(b-a);
line[i].l=p.x-p.y*tan(a+b);
//   printf("%d : %lf~%lf\n",i,p.y*tan(b-a),p.y*tan(b+a));
}
sort(line+1,line+1+n);
double L=line[1].l,R=line[1].r;
for (int i=2;i<=n;i++)
{
if (line[i].l>R)
{
printf("%.2f %.2f\n",L,R);
L=line[i].l,R=line[i].r;
}
else R=max(R,line[i].r);
}
printf("%.2f %.2f\n\n",L,R);
}

return 0;
}