POJ 1375

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>

using namespace std;
const int MAX=1050;

struct point{
double x;
int flag;
point(){ flag=0;}
}p[MAX];

double dist(double x1,double y1,double x2,double y2){
return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

bool cmp(point A, point B){
if(A.x<B.x)return true;
else if(A.x==B.x){
if(A.flag<B.flag) return true;
}
return false;
}

int main(){
double lx,ly; int n; double x,y,r;
while(scanf("%d",&n)!=EOF){
if(n==0) break;
scanf("%lf%lf",&lx,&ly);
for(int i=0;i<n;i++){
scanf("%lf%lf%lf",&x,&y,&r);
double dis=dist(lx,ly,x,y);
double Agle=asin(r/dis); double Bgle=asin((lx-x)/dis);
double bx=lx-ly*tan(Agle+Bgle);
double ex=lx-ly*tan(Bgle-Agle);
p[2*i].x=bx; p[2*i].flag=-1;
p[2*i+1].x=ex; p[2*i+1].flag=1;
}
sort(p,p+2*n,cmp);
int now=0; double L;
for(int i=0;i<2*n;i++){
if(now==0){
L=p[i].x;
}
now+=p[i].flag;
if(now==0)
printf("%0.2f %0.2f\n",L,p[i].x);
}
printf("\n");
}
return 0;
}