hdu 1077 Catching Fish 计算几何+暴力枚举

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简单的暴力枚举，枚举两个点在圆上，用向量法求下圆心。复杂度o(n^3)，但数据量只有300

/*author:jxylang: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 1E9using 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);    }}