hdu 1077 Catching Fish 计算几何+暴力枚举

/*
author:jxy
lang:C/C++
university:China,Xidian University
**If you need to reprint,please indicate the source**
*/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#define INF 1E9
using namespace std;
double X[301],Y[301];
int n,ans;
double x,y;
inline double c(int i)
{
return (X[i]-x)*(X[i]-x)+(Y[i]-y)*(Y[i]-y);
}
int calc()//计数
{
int i,ans=0;
for(i=0;i<n;i++)
{
if(c(i)>1.0+1e-8)continue;
ans++;
}
return ans;
}
void center(int i,int j)//确定圆心
{
double x1=X[i]-X[j],y1=Y[i]-Y[j],len,k;
double a,b;//单位向量
if(x1==0)
a=1,b=0;
else if (y1==0)
a=0,b=1;
else
{
k=-1/y1*x1;
len=sqrt(1+k*k);
a=1.0/len;
b=k/len;
}
len=1-(x1*x1+y1*y1)/4;
if(len<0)return;
len=sqrt(len);
x1=(X[i]+X[j])/2.0;y1=(Y[i]+Y[j])/2.0;
a*=len;b*=len;
x=x1+a;y=y1+b;
ans=max(ans,calc());
x=x1-a;y=y1-b;
ans=max(ans,calc());
}
int main()
{
int T;
int i,j;
scanf("%d",&T);
while(T--)
{
scanf("%d",&n);
for(i=0;i<n;i++)
scanf("%lf%lf",&X[i],&Y[i]);
ans=0;
for(i=0;i<n;i++)
for(j=i;j<n;j++)
center(i,j);
printf("%d\n",ans);
}
}