POJ 3675 Telescope

Test instructions: Given a polygon that is not self-intersection, the area of the circle at the origin is required and the center of the circle is intersection.

Ideas: With POJ2986, is the enhanced version

Code:

1#include <algorithm>2#include <cstdio>3#include <cmath>4#include <cstring>5#include <iostream>6 structpoint{7     Doublex, y;8 Point () {}9Point (DoubleX0,Doubley0): X (x0), Y (y0) {}Ten}p[200005],a[5],o; One structline{ A Point s,e; - Line () {} - Line (Point S0,point E0): S (s0), E (E0) {} the }; - intN; - DoubleR; - Const Doubleeps=1e-8; + Const DoublePi=acos (-1); - DoubleSgnDoublex) { +     if(x>eps)return 1.0; A     if(x<-eps)return-1.0; at     return 0; - } -Pointoperator* (Point P1,Doublex) { -     returnPoint (p1.x*x,p1.y*x); - } -Pointoperator/(Point P1,Doublex) { in     returnPoint (p1.x/x,p1.y/x); - } to Double operator/(Point p1,point p2) { +     returnp1.x*p2.x+p1.y*p2.y; - } the Double operator*(Point p1,point p2) { *     returnp1.x*p2.y-p1.y*p2.x; $ }Panax NotoginsengPointoperator+(Point p1,point p2) { -     returnPoint (p1.x+p2.x,p1.y+p2.y); the } +Pointoperator-(Point p1,point p2) { A     returnPoint (p1.x-p2.x,p1.y-p2.y); the } + Doubledis (point p1) { -     returnsqrt (p1.x*p1.x+p1.y*p1.y); $ } $ Doubledis (point p1,point p2) { -     returnDis (Point (p1.x-p2.x,p1.y-p2.y)); - } the DoubleSqrDoublex) { -     returnx*x;Wuyi } the DoubleDist_line (line p) { -     Doublea,b,c,dist; Wua=p.s.y-p.e.y; -b=p.s.x-p.e.x; Aboutc=p.s.x*p.e.y-p.s.y*p.e.x; $Dist=fabs (C)/sqrt (SQR (A) +Sqr (B)); -     returnDist; - } - DoubleGet_cos (DoubleADoubleBDoublec) { A     return(b*b+c*c-a*a)/(2*b*c); + } the DoubleGet_angle (Point p1,point p2) { -     if(!SGN (Dis (p1)) | |! SGN (Dis (p2)))return 0.0; $     Doublea,b,c; theA=dis (p1); theb=dis (p2); theC=dis (P1,P2); the     if(c<=eps)return 0.0; -     returnACOs (Get_cos (c,a,b)); in } the Point Get_point (point p) { the     DoubleT=SQR (p.x) +Sqr (P.Y); About     returnPoint (SGN (p.x) *sqrt (SQR (p.x)/T), SGN (P.Y) *sqrt (SQR (P.Y)/T)); the } the DoubleS (Point p1,point p2,point p3) { the     returnFabs ((P2-P1) * (P3-P1))/2; + } - DoubleWork (Point p1,point p2) { the     DoubleF=SGN (P1*P2), res=0;Bayi     if(!SGN (f) | |! SGN (Dis (p1)) | |! SGN (Dis (p2)))return 0.0; the     DoubleL=Dist_line (Line (P1,P2)); the     DoubleA=dis (p1); -     Doubleb=dis (p2); -     DoubleC=dis (P1,P2); the     if(a<=r&&b<=R) { the         returnFabs (P1*P2)/2.0*F; the     } the     if(a>=r&&b>=r&&l>=R) { -         Doubleang=Get_angle (P1,P2); the         returnFabs ((ang/(2.0)) * (R*R)) *F; the     } the     if(a>=r&&b>=r&&l<=r&& (Get_cos (a,b,c) <=0|| Get_cos (b,a,c) <=0)){94         Doubleang=Get_angle (P1,P2); the         returnFabs ((ang/(2.0)) * (R*R)) *F; the     } the     if(a>=r&&b>=r&&l<=r&& (Get_cos (a,b,c) >0&&get_cos (B,A,C) >0)){98         Doubledist=Dist_line (Line (P1,P2)); About         DoubleLen=sqrt (Sqr (R)-SQR (dist)) *2.0; -         Doubleang1=Get_angle (P1,P2);101         DoubleCos2=Get_cos (len,r,r);102Res+=fabs (len*dist/2.0);103         DoubleAng2=ang1-ACOs (COS2);104Res+=fabs ((ang2/(2)) * (r*R)); the         returnRes*F;106     }107     if((a>=r&&b<r) | | (a<r&&b>=s)) {108         if(b>a) Std::swap (A, B), Std::swap (P1,P2);109         DoubleT=SQR (p1.x-p2.x) +SQR (p1.y-p2.y); thePoint U=point (SGN (p1.x-p2.x) *sqrt (SQR (p1.x-p2.x)/T), SGN (P1.Y-P2.Y) *sqrt (SQR (P1.Y-P2.Y)/T));111         Doubledist=Dist_line (Line (P1,P2)); the         DoubleLEN=SQRT (r*r-dist*Dist);113         DoubleLen2=sqrt (Sqr (Dis (p2))-Sqr (Dist)); the         if(Fabs (DIS (p2+u*len2)-dist) <=eps) len+=Len2; the         Elselen-=Len2; thePoint p=p2+u*Len;117res+=S (o,p2,p);118         Doubleang=Get_angle (p1,p);119Res+=fabs ((ang/2.0) *r*R); -         returnRes*F;121     }122     return 0;123 }124 intMain () { theO=point (0,0);126      while(SCANF ("%LF", &r)! =EOF) {127scanf"%d",&n); -          for(intI=1; i<=n;i++)129scanf"%LF%LF",&p[i].x,&p[i].y); thep[n+1]=p[1];131         Doubleans=0; the          for(intI=1; i<=n;i++)133Ans+=work (p[i],p[i+1]);134ans=fabs (ans); 135printf"%.2f\n", ans); 136     }137}

POJ 3675 Telescope