The area of the Union of Circles

#include <stdio.h> #include <math.h> #include <algorithm>using namespace Std;const double eps=1e-8;    Const double Pi=acos ( -1.0); struct circle{double x,y,r; Circle () {} circle (double xx,double yy) {x=xx;y=yy;}};    struct node{//in point +1, which can indicate how many layers of double angle are covered;    int flag; Node () {} node (double A,int b) {angle=a;flag=b;}}; Circle c[1005]; Node p[2005];d ouble ss[100];int n;double Dist (Circle a,circle b) {return sqrt ((a.x-b.x) * (a.x-b.x) + (A.Y-B.Y) * (A.Y-B.Y)) ;} int cmp (Circle a,circle b) {return A.R&LT;B.R;}    void Init () {sort (c,c+n,cmp);    int cnt; for (int i=1,j=0;i<n;i++) {//Remove inner-cut and included circles if (c[i].x==c[j].x && c[i].y==c[j].y | |        C[i].r<eps) continue;        if ((C[I].R-C[J].R) <dist (C[i],c[j]) +eps) c[++j]=c[i];    cnt=j+1; } n=cnt;}    void Getarc (Circle p,circle q,double &a,double &b) {//a is a small corner, B is a large angle double d=dist (P,Q);    Double Tmp1=acos ((D*D+P.R*P.R-Q.R*Q.R)/(2*D*P.R));    Double tmp2=atan2 (q.y-p.y,q.x-p.x);    A=TMP2-TMP1; b=TMP1+TMP2;    if (B&GT;PI) B-=2*pi;    if (A&LT;-PI) A+=2*pi;    printf ("%lf%f\n", A, b); printf ("%f\n", TMP2);}    int Cmp1 (Node A,node b) {if (A.angle!=b.angle) return a.angle<b.angle; else return a.flag>b.flag;} Double Cross (Circle a,circle b) {return a.x*b.y-a.y*b.x;} Double Getarea (double a,double r) {return r*r* (a/2.0);}    void Solve () {double area=0;        for (int i=0;i<n;i++) {int cnt=0,flag=0; for (int j=0;j<n;j++) {if (I==j | |            C[i].r+c[j].r<dist (C[i],c[j]) +eps) continue;//does not intersect directly skips double A, b;            Getarc (C[I],C[J],A,B); P[cnt++]=node (a,1);    P[cnt++]=node (b,-1);//a is a small corner, B is a large angle if (a>b) flag++;//record the leftmost point of the circle is covered how many times} p[cnt++]=node (-pi,flag);        P[cnt++]=node (Pi,-flag);        Sort (P,P+CNT,CMP1);                int s=flag+1;//+1 is because each segment arc is at least c[i] this circle overrides for (int j=1;j<cnt;j++) {if (s==1) {//is covered 1 times and above the area                Circle A, B; A.x=c[i].x+c[i].r*cos (P[j-1].angle); A.y=c[i].y+c[i].r*sin (P[j-1].angle); B.x=c[i].x+c[i].r*cos (P[j].angle);                B.y=c[i].y+c[i].r*sin (P[j].angle);                Double K=p[j].angle-p[j-1].angle;         area+= (K-sin (k)) *c[i].r*c[i].r*0.5;//Bow Area Area+=cross (A, B) *0.5;//area} S+=p[j].flag; }} printf ("%f\n", area);}    int main () {#ifndef Online_judge freopen ("In.txt", "R", stdin); #endif//Online_judge while (scanf ("%d", &n)!=eof) {for (int i=0;i<n;i++) scanf ("%lf%lf%lf", &c[i].x,&am        P;C[I].Y,&AMP;C[I].R);        Init ();    Solve (); } return 0;}

The area of the Union of Circles