题解：P14433 [JOISC 2013] JOI 海报 / JOI Poster

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define p_q priority_queue
#define pb push_back
#define mk make_pair
#define pii pair<int,int> 
#define ve vector
#define endl '\n'
#define fi first
#define se second
#define INF 0x3f3f3f3f
#define eps 1e-10
#define lowbit(x) (x&(-x))
namespace cute_fzj_kuai_ruarua{
	double dis(int x,int y,int xx,int yy){
		return sqrt((x-xx)*(x-xx)+(y-yy)*(y-yy));
	}
	int k;
	int n,m;
	int x[55],y[55];
	void main(){
		cin>>k>>n>>m;
		for(int i=1;i<=k;i++){
			cin>>x[i]>>y[i];
		}
		int ans=0;
		for(int A=1;A<=k;A++){
			for(int B=1;B<=k;B++){
				for(int C=1;C<=k;C++){
					for(int D=1;D<=k;D++){
						if(A==B||A==C||A==D||B==C||B==D||C==D) continue;
						double r=dis(x[A],y[A],x[B],y[B]);
						double R=dis(x[C],y[C],x[D],y[D]);
						if(x[A]-r<-eps||x[A]+r-n>eps||y[A]-r<-eps||y[A]+r-m>eps) continue;
						if(x[C]-R<-eps||x[C]+R-n>eps||y[C]-R<-eps||y[C]+R-m>eps) continue;
						if(eps<r-R-dis(x[A],y[A],x[C],y[C])) ans++;
					}
				}
			}
		}
		cout<<ans;
	}
} 
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cute_fzj_kuai_ruarua::main(); 
	return 0;
}