hdu4720Naive and Silly Muggles

链接

一直理解的最小覆盖圆就是外接圆。。原来还要分钝角和锐角。。。

钝角的话就为最长边的中点，对于这题分别枚举一下外接圆以及中点的圆，判一下是不是在园外。

  1 #include <iostream>

  2 #include<cstdio>

  3 #include<cstring>

  4 #include<algorithm>

  5 #include<stdlib.h>

  6 #include<vector>

  7 #include<cmath>

  8 #include<queue>

  9 #include<set>

 10 using namespace std;

 11 #define N 100000

 12 #define LL long long

 13 #define INF 0xfffffff

 14 const double eps = 1e-8;

 15 const double pi = acos(-1.0);

 16 const double inf = ~0u>>2;

 17 struct Point

 18 {

 19     double x,y;

 20     Point (double x=0,double y =0):x(x),y(y){}

 21 }p[4];

 22 struct Circle

 23 {

 24     Point center;

 25     double r;

 26 };

 27 typedef Point pointt;

 28 pointt operator - (Point a,Point b)

 29 {

 30     return Point(a.x-b.x,a.y-b.y);

 31 }

 32 int dcmp(double x)

 33 {

 34     if(fabs(x)<eps) return 0;

 35     return x<0?-1:1;

 36 }

 37 double dis(Point a)

 38 {

 39     return a.x*a.x+a.y*a.y;

 40 }

 41 double cross(Point a,Point b)

 42 {

 43     return a.x*b.y-a.y*b.x;

 44 }

 45 double area()

 46 {

 47     return fabs(cross(p[1]-p[2],p[2]-p[3]))/2;

 48 }

 49 struct Circle Circumcircle()

 50 {

 51     Circle tmp;

 52     double a,b,c,c1,c2;

 53     double xa,ya,xb,yb,xc,yc;

 54     a = sqrt(dis(p[3]-p[1]));

 55     b = sqrt(dis(p[1]-p[2]));

 56     c = sqrt(dis(p[2]-p[3]));

 57     //¸ù¾Ýs = a*b*c/R/4£¬Çó°ë¾¶

 58     tmp.r = (a*b*c)/(area()*4.0);

 59     xa = p[3].x;

 60     ya = p[3].y;

 61     xb = p[1].x;

 62     yb = p[1].y;

 63     xc = p[2].x;

 64     yc = p[2].y;

 65     c1 = (dis(p[3])-dis(p[1]))/2;

 66     c2 = (dis(p[3])-dis(p[2]))/2;

 67     tmp.center.x = (c1*(ya-yc)-c2*(ya-yb))/((xa-xb)*(ya-yc)-(xa-xc)*(ya-yb));

 68     tmp.center.y = (c1*(xa-xc)-c2*(xa-xb))/((ya-yb)*(xa-xc)-(ya-yc)*(xa-xb));

 69     return tmp;

 70 }

 71 int main()

 72 {

 73     int t,i;

 74     cin>>t;

 75     int kk = 0;

 76     while(t--)

 77     {

 78         for(i = 1 ;i <= 3 ; i++)

 79         scanf("%lf%lf",&p[i].x,&p[i].y);

 80         Circle cc = Circumcircle();

 81         Point pp;

 82         scanf("%lf%lf",&pp.x,&pp.y);

 83         double r = cc.r;

 84         r*=r;

 85         printf("Case #%d: ",++kk);

 86         if(dis(pp-cc.center)>r)

 87         {

 88             puts("Safe");

 89             continue;

 90         }

 91         r = dis(p[1]-p[2])/4;

 92         cc.center.x = (p[1].x+p[2].x)/2;

 93         cc.center.y = (p[1].y+p[2].y)/2;

 94         if(dcmp(dis(p[3]-cc.center)-r)<=0&&dcmp(dis(pp-cc.center)-r)>0)

 95         {

 96             puts("Safe");

 97             continue;

 98         }

 99         r = dis(p[1]-p[3])/4;

100         cc.center.x = (p[1].x+p[3].x)/2;

101         cc.center.y = (p[1].y+p[3].y)/2;

102         if(dcmp(dis(p[2]-cc.center)-r)<=0&&dcmp(dis(pp-cc.center)-r)>0)

103         {

104             puts("Safe");

105             continue;

106         }

107         r = dis(p[3]-p[2])/4;

108         cc.center.x = (p[3].x+p[2].x)/2;

109         cc.center.y = (p[3].y+p[2].y)/2;

110         if(dcmp(dis(p[1]-cc.center)-r)<=0&&dcmp(dis(pp-cc.center)-r)>0)

111         {

112             puts("Safe");

113             continue;

114         }

115         puts("Danger");

116     }

117     return 0;

118 }

View Code