delete pics to save space

2.11168.cpp

@@ -0,0 +1,108 @@
+#include<cstdio>
+#include<cstdlib>
+#include<cmath>
+#include<vector>
+#include<algorithm>
+using std::sort;
+
+struct Point
+{
+	double x,y;
+	Point(double x=0,double y=0):x(x),y(y){}
+};
+typedef Point Vector;
+
+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 ops=1e-10;
+inline int dcmp(double x)
+{ return (x>0?x:-x)<ops?0:(x>0?1:-1); }
+
+const double Pi=atan(1)*4;
+inline double D_to_R(double D)
+{ return Pi/180*D; }
+
+inline double Cross(const Vector &A,const Vector &B)
+{ return A.x*B.y-A.y*B.x; }
+
+inline Vector Rotate(const Vector &A,double rad)
+{
+	double csr=cos(rad),sir=sin(rad);
+	return Vector(A.x*csr-A.y*sir,A.x*sir+A.y*csr);
+}
+
+inline double PolygonArea(Point* p,int n)
+{
+	double area=0;
+	for(int i=1;i<n-1;i++)
+		area+=Cross(p[i]-p[0],p[i+1]-p[0]);
+	return area/2;
+}
+int ConvexHull(Point *p,int n,Point *ch)
+{
+	sort(p,p+n);
+	int m=0;
+	for(int i=0;i<n;i++)
+	{
+		while(m>1&&Cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0) m--;
+		ch[m++]=p[i];
+	}
+	int k=m;
+	for(int i=n-2;i>=0;i--)
+	{
+		while(m>k&&Cross(ch[m-1]-ch[m-2],p[i]-ch[m-2])<=0) m--;
+		ch[m++]=p[i];
+	}
+	if(n>1) m--;
+	return m;
+}
+using namespace std;
+int T,n,m;
+double sumx,sumy,res;
+Point p[10005],ch[10005];
+double X1,Y1,X2,Y2;
+double A,B,C;
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%d",&T);
+	for(int kase=1;kase<=T;kase++)
+	{
+		scanf("%d",&n);
+		sumx=0;sumy=0;
+		for(int i=0;i<n;i++)
+		{
+			scanf("%lf%lf",&p[i].x,&p[i].y);
+			sumx+=p[i].x;
+			sumy+=p[i].y;
+		}
+		m=ConvexHull(p,n,ch);
+		res=1e20;
+		if(m<=2) res=0;
+		else for(int i=0;i<m;i++)
+		{
+			X1=ch[i].x;Y1=ch[i].y;X2=ch[(i+1)%m].x;Y2=ch[(i+1)%m].y;
+			A=Y2-Y1;
+			B=X1-X2;
+			C=X2*Y1-X1*Y2;
+			res=min(res,fabs(A*sumx+B*sumy+C*n)/sqrt(A*A+B*B));
+		}
+		printf("Case #%d: %.3lf\n",kase,res/n);
+	}
+	return 0;
+}