HDU-4720 Naive and Silly Muggles 圆的外心
题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4720
先两两点之间枚举，如果不能找的最小的圆，那么求外心即可。。
1 //STATUS:C++_AC_0MS_292KB 2 #include <functional> 3 #include <algorithm> 4 #include <iostream> 5 //#include <ext/rope> 6 #include <fstream> 7 #include <sstream> 8 #include <iomanip> 9 #include <numeric> 10 #include <cstring> 11 #include <cassert> 12 #include <cstdio> 13 #include <string> 14 #include <vector> 15 #include <bitset> 16 #include <queue> 17 #include <stack> 18 #include <cmath> 19 #include <ctime> 20 #include <list> 21 #include <set> 22 #include <map> 23 using namespace std; 24 //#pragma comment(linker,"/STACK:102400000,102400000") 25 //using namespace __gnu_cxx; 26 //define 27 #define pii pair<int,int> 28 #define mem(a,b) memset(a,b,sizeof(a)) 29 #define lson l,mid,rt<<1 30 #define rson mid+1,r,rt<<1|1 31 #define PI acos(-1.0) 32 //typedef 33 typedef __int64 LL; 34 typedef unsigned __int64 ULL; 35 //const 36 const int N=25; 37 const int INF=0x3f3f3f3f; 38 const int MOD=1000000007,STA=8000010; 39 const LL LNF=1LL<<60; 40 const double EPS=1e-8; 41 const double OO=1e60; 42 const int dx[4]={-1,0,1,0}; 43 const int dy[4]={0,1,0,-1}; 44 const int day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31}; 45 //Daily Use ... 46 inline int sign(double x){return (x>EPS)-(x<-EPS);} 47 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;} 48 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;} 49 template<class T> inline T lcm(T a,T b,T d){return a/d*b;} 50 template<class T> inline T Min(T a,T b){return a<b?a:b;} 51 template<class T> inline T Max(T a,T b){return a>b?a:b;} 52 template<class T> inline T Min(T a,T b,T c){return min(min(a, b),c);} 53 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);} 54 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));} 55 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));} 56 //End 57 58 int T; 59 60 struct Point{ 61 double x,y; 62 }p[5]; 63 64 double dist(Point a,Point b) 65 { 66 return sqrt( (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y) ); 67 } 68 69 double sqr(double x){ return x * x; } 70 71 void Ci(Point p0 , Point p1 , Point p2 , Point &cp) 72 { 73 double a1=p1.x-p0.x,b1 = p1.y - p0.y,c1 = (sqr(a1) + sqr(b1)) / 2; 74 double a2=p2.x-p0.x,b2 = p2.y - p0.y,c2 = (sqr(a2) + sqr(b2)) / 2; 75 double d = a1 * b2 - a2 * b1; 76 cp.x = p0.x + (c1 * b2 - c2 * b1) / d; 77 cp.y = p0.y + (a1 * c2 - a2 * c1) / d; 78 } 79 80 int judge1(int& ok) 81 { 82 int i,j,k; 83 double d,r,lowr; 84 Point c,t; 85 lowr=OO; 86 for(i=0;i<3;i++){ 87 for(j=0;j<3;j++){ 88 if(i==j)continue; 89 r=dist(p[i],p[j])/2; 90 t.x=(p[i].x+p[j].x)/2; 91 t.y=(p[i].y+p[j].y)/2; 92 for(k=0;k==i || k==j;k++); 93 if(dist(t,p[k])<=r){ 94 lowr=r; 95 c.x=t.x,c.y=t.y; 96 } 97 } 98 } 99 if(lowr==OO)return 0; 100 if(dist(p[3],c)<=lowr)ok=1; 101 return 1; 102 } 103 104 int main(){ 105 // freopen("in.txt","r",stdin); 106 int i,j,ca=1,ok; 107 double r,d; 108 Point c; 109 scanf("%d",&T); 110 while(T--) 111 { 112 for(i=0;i<4;i++){ 113 scanf("%lf%lf",&p[i].x,&p[i].y); 114 } 115 ok=0; 116 if(judge1(ok)); 117 else { 118 Ci(p[0],p[1],p[2],c); 119 r=(c.x-p[0].x)*(c.x-p[0].x)+(c.y-p[0].y)*(c.y-p[0].y); 120 d=(c.x-p[3].x)*(c.x-p[3].x)+(c.y-p[3].y)*(c.y-p[3].y); 121 if(d<=r)ok=1; 122 } 123 124 printf("Case #%d: %s\n",ca++,ok?"Danger":"Safe"); 125 } 126 return 0; 127 }
