delete pics to save space

2.1308.cpp

@@ -0,0 +1,127 @@
+#include<cstdio>
+#include<cstring>
+#include<cstdlib>
+#include<cmath>
+#include<vector>
+#include<algorithm>
+struct Point
+{
+	double x,y;
+	Point(double x=0,double y=0):x(x),y(y){}
+};
+typedef Point Vector;
+
+inline Point read_point()
+{
+	Point A;
+	scanf("%lf%lf",&A.x,&A.y);
+	return A;
+}
+
+inline Vector operator+(const Vector &A,const Vector &B)
+{ return Vector(A.x+B.x,A.y+B.y); }
+
+inline Vector operator-(const Point &a,const Point &b)
+{ return Vector(a.x-b.x,a.y-b.y); }
+
+inline Vector operator*(const Vector &A,double p)
+{ return Vector(A.x*p,A.y*p); }
+
+inline Vector operator/(const Vector &A,double p)
+{ return Vector(A.x/p,A.y/p); }
+
+inline bool operator<(const Point &a,const Point &b)
+{ return a.x<b.x||(a.x==b.x&&a.y<b.y); }
+
+const double Pi=acos(-1);
+const double eps=5e-13;
+inline int dcmp(double x)
+{ return (x>0?x:-x)<eps?0:(x>0?1:-1); }
+
+inline bool operator==(const Point &a,const Point &b)
+{ return dcmp(a.x-b.x)==0&&dcmp(a.y-b.y)==0; }
+
+inline double Dot(const Vector &A,const Vector &B)
+{ return A.x*B.x+A.y*B.y; }
+
+inline double Length(const Vector &A)
+{ return sqrt(Dot(A,A)); }
+
+inline double Angle(const Vector &A)
+{ return atan2(A.y,A.x); }
+
+struct Circle
+{
+	Point c;
+	double r;
+	Circle(Point c=Point(),double r=0):c(c),r(r){}
+	inline Point point(double a,double delta)
+	{ return Point(c.x+cos(a)*(r+delta),c.y+sin(a)*(r+delta)); }
+};
+inline Circle read_circle()
+{
+	Circle C;
+	scanf("%lf%lf%lf",&C.c.x,&C.c.y,&C.r);
+	return C;
+}
+using namespace std;
+int n;
+Circle c[105];
+bool cansee[105],flag;
+inline bool in(const Point &p,const Circle &c)
+{ return dcmp(Length(c.c-p)-c.r)<=0; }
+vector<double> ang;
+void intersectangle(int i,int j)
+{
+    double d=Length(c[i].c-c[j].c);
+    if (dcmp(d-fabs(c[i].r-c[j].r))<=0
+	||dcmp(d-c[i].r-c[j].r)>=0) return;
+    double x=Angle(c[j].c-c[i].c),
+	y=acos((c[i].r*c[i].r+d*d-c[j].r*c[j].r)/2/c[i].r/d);
+    ang.push_back(x+y);
+    ang.push_back(x-y);
+}
+void mark(const Point &p)
+{
+	for(int i=n-1;i>=0;i--)
+		if(in(p,c[i]))
+		{
+			cansee[i]=true;
+			return;
+		}
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	while(scanf("%d",&n)==1&&n)
+	{
+		for(int i=0;i<n;i++) c[i]=read_circle();
+		memset(cansee,0,sizeof(cansee));
+		for(int i=0;i<n;i++)
+		{
+			ang.clear();
+			for(int j=0;j<n;j++)
+				if(i!=j)
+					intersectangle(i,j);
+			if(ang.empty())
+			{
+				mark(c[i].point(0,eps));
+				mark(c[i].point(0,-eps));
+				continue;
+			}
+			sort(ang.begin(),ang.end());
+			for(int j=0;j<ang.size();j++)
+			{
+				double x=(ang[j]+ang[(j+1)%n])/2;
+				mark(c[i].point(x,eps));
+				mark(c[i].point(x,-eps));
+			}
+		}
+		int res=0;
+		for(int i=0;i<n;i++) res+=cansee[i];
+		printf("%d\n",res);
+	}
+	return 0;
+}