codeforce--600D - Area of Two Circles' Intersection
题意：求相交圆的面积。借鉴大神代码，精度超高。
1 #include <fstream> 2 #include <iostream> 3 #include <string> 4 #include <complex> 5 #include <math.h> 6 #include <set> 7 #include <vector> 8 #include <map> 9 #include <queue> 10 #include <stdio.h> 11 #include <stack> 12 #include <algorithm> 13 #include <list> 14 #include <ctime> 15 #include <memory.h> 16 #include <ctime> 17 #include <assert.h> 18 19 #define y1 aasdfasdfasdf 20 21 #define eps 1e-16 22 #define M_PI 3.141592653589793 23 const int N = 200005; 24 using namespace std; 25 26 long double x1,y1,x2,y2,r1,r2; 27 28 long double gd(long double x1,long double y1,long double x2,long double y2) 29 { 30 return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)); 31 } 32 33 long double solve_cos(long double a,long double b,long double c) 34 { 35 return acos((a*a+b*b-c*c)/(2*a*b)); 36 } 37 38 long double cut(long double ang,long double r) 39 { 40 long double s1,s2; 41 s1=ang*r*r/2; 42 s2=sin(ang)*r*r/2; 43 return s1-s2; 44 } 45 46 long double solve() 47 { 48 if (r1<r2) 49 { 50 swap(x1,x2); 51 swap(y1,y2); 52 swap(r1,r2); 53 } 54 long double cd=gd(x1,y1,x2,y2); 55 if (cd+r2<=r1+eps) 56 return r2*r2*M_PI; 57 if (cd>=r1+r2-eps) 58 return 0; 59 long double ang1=solve_cos(cd,r1,r2); 60 long double ang2=solve_cos(cd,r2,r1); 61 return cut(ang1*2,r1)+cut(ang2*2,r2); 62 } 63 64 int main() 65 { 66 cin>>x1>>y1>>r1; 67 cin>>x2>>y2>>r2; 68 cout.precision(12); 69 cout<<fixed<<solve()<<endl; 70 return 0; 71 }
