zstu-4243 牛吃草

贴一发两圆相交面积模板

 1 #include<bits/stdc++.h>
 2 #define pi acos(-1.0)
 3 using namespace std;
 4 const double eps=1e-6;
 5 double _abs(double x)
 6 {
 7     if(x<0) return -x;
 8     else return x;
 9 }
10 struct point
11 {
12     point(double _x=0,double _y=0){x=_x; y=_y;}
13     double x,y;
14 }p1,p2;
15 double R;
16 double AREA(point a, double r1, point b, double r2)
17 {
18     double d=sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
19     if(d>=r1+r2) return 0;
20     if(r1>r2)
21     {
22         double tmp=r1;
23         r1=r2;
24         r2=tmp;
25     }
26     if(r2-r1>=d)
27         return pi*r1*r1;
28     double ang1=acos((r1*r1+d*d-r2*r2)/(2*r1*d));
29     double ang2=acos((r2*r2+d*d-r1*r1)/(2*r2*d));
30     return ang1*r1*r1+ang2*r2*r2-r1*d*sin(ang1);
31 }
32 int main()
33 {
34     int T; scanf("%d",&T);
35     while(T--)
36     {
37         scanf("%lf%lf%lf%lf%lf",&p1.x,&p1.y,&p2.x,&p2.y,&R);
38         double l=0,r=1000000,area=pi*R*R/2;
39         while(_abs(l-r)>eps)
40         {
41             double mid=(l+r)/2;
42             if(AREA(p1,R,p2,mid)>=area) r=mid;
43             else l=mid;
44         }
45         printf("%.4f\n",l);
46     }
47     return 0;
48 }
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posted @ 2017-11-21 15:32  NotNight  阅读(154)  评论(0)  编辑  收藏  举报