bzoj4642: 泡泡

#include<cstdio>
#include<algorithm>
#include<cmath>
#include<set>
typedef long double ld;
const ld _0=1e-8,_s=std::sin(0.43415),_c=std::cos(0.43415);
int ans=0;
struct cir{
    ld x,y,r;
}cs[500010];
struct event{
    ld x;
    int id,type;
}es[1000010];
std::pair<int,int>as[1500050];
int ap=0;
bool operator<(event a,event b){
    return a.x<b.x;
}
struct cmp{bool operator()(int x,int y){return cs[x].y<cs[y].y;}};
std::set<int,cmp>line;
void chk(int a,int b){
    ld x=cs[a].x-cs[b].x,y=cs[a].y-cs[b].y;
    if(std::fabs(std::sqrt(x*x+y*y)-cs[a].r-cs[b].r)<_0){
        if(a>b){int c=a;a=b;b=c;}
        as[ap++]=std::make_pair(a,b);
    }
}
int main(){
    int n=_int();
    for(int i=0;i<n;i++){
        int x,y,r;
        scanf("%d%d%d",&x,&y,&r);
        cs[i].x=_c*x+_s*y;
        cs[i].y=-_s*x+_c*y;
        cs[i].r=r;
        es[i<<1]=(event){cs[i].x-cs[i].r,i,1};
        es[i<<1^1]=(event){cs[i].x+cs[i].r,i,0};
    }
    n<<=1;
    std::sort(es,es+n);
    for(int i=0;i<n;i++){
        event w=es[i];
        if(w.type){
            std::set<int,cmp>::iterator it=line.upper_bound(w.id);
            if(it!=line.end())chk(*it,w.id);
            if(it!=line.begin())--it,chk(*it,w.id);
            line.insert(w.id);
        }else{
            std::set<int,cmp>::iterator it=line.find(w.id);
            if(it!=line.begin()){
                int a=*--it;++it;++it;
                if(it!=line.end())chk(*it,a);
                --it;
            }
            line.erase(it);
        }
    }
    std::sort(as,as+ap);
    if(ap)ans=1;
    for(int i=1;i<ap;i++)if(as[i]!=as[i-1])++ans;
    printf("%d\n",ans);
    return 0;
}