牛吃草（二分）

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题目链接：点击打开链接

代码：

#include<stdio.h>#include<math.h>#define pi acos(-1.0)#define inf 10000000struct circle{    double x,y;    double r;} c1,c2;double  get_juli(double x1,double y1,double x2,double y2){    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));}double get_mianji(circle c1,circle c2){    double dis=get_juli(c1.x,c1.y,c2.x,c2.y);    if(dis>=c1.r+c2.r)        return 0;    double min_r=c1.r<c2.r?c1.r:c2.r;    double max_r=c1.r>c2.r?c1.r:c2.r;    if(min_r+dis<=max_r)        return pi*min_r*min_r;    double  a=acos((c1.r*c1.r+dis*dis-c2.r*c2.r)/2/c1.r/dis);    double b=acos((c2.r*c2.r+dis*dis-c1.r*c1.r)/2/c2.r/dis);    double area1=a*c1.r*c1.r;    double area2=b*c2.r*c2.r;    double ans=area1+area2;    double area_que=sin(a)*c1.r*dis;    ans-=area_que;    return ans;}int main(){    int q;    scanf("%d",&q);    while(q--)    {//        double x0,y0,x1,y1,r;        scanf("%lf%lf%lf%lf%lf",&c1.x,&c1.y,&c2.x,&c2.y,&c1.r);        double mianji=pi*c1.r*c1.r/2.0;        double l=0,r=inf,mid;        while(r-l>=1e-9)        {            mid=(r+l)/2.0;            c2.r=mid;            if(get_mianji( c1, c2)>=mianji)                r=mid;            else                l=mid;        }        printf("%.4lf\n",r);    }}

time：16ms, memory:980kb;

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