poj2187 Beauty Contest
求平面上距离最远的两个点距离的平方。
凸包，旋转卡壳。
抄板选手的日常。
1 //Achen 2 #include<algorithm> 3 #include<iostream> 4 #include<cstring> 5 #include<cstdlib> 6 #include<vector> 7 #include<cstdio> 8 #include<queue> 9 #include<cmath> 10 typedef long long LL; 11 typedef double db; 12 const db eps=1e-10; 13 const int N=50007; 14 using namespace std; 15 int n; 16 17 template<typename T>void read(T &x) { 18 char ch=getchar(); x=0; T f=1; 19 while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar(); 20 if(ch=='-') f=-1,ch=getchar(); 21 for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0'; x*=f; 22 } 23 24 struct pt { 25 db x,y; 26 pt(db x=0,db y=0):x(x),y(y){} 27 }p[N],q[N]; 28 typedef pt vc; 29 30 vc operator + (vc A,vc B) { return vc(A.x+B.x,A.y+B.y);} 31 vc operator - (vc A,vc B) { return vc(A.x-B.x,A.y-B.y);} 32 bool operator <(const vc&A,const vc&B) { return A.x<B.x||(A.x==B.x&&A.y<B.y);} 33 int dcmp(double x) { if(fabs(x)<eps) return 0; else return x<0?-1:1;} 34 bool operator == (const vc&A,const vc&B) { return dcmp(A.x-B.x)==0&&dcmp(A.y-B.y)==0; } 35 36 db dot(vc A,vc B) { return A.x*B.x+A.y*B.y; } 37 db length(vc A) { return dot(A,A); } 38 db cross(vc A,vc B) { return A.x*B.y-A.y*B.x; } 39 40 bool cmp(const pt &A,const pt&B) { 41 return dcmp(cross(A-p[1],B-p[1]))==0?length(A-p[1])<length(B-p[1]):cross(A-p[1],B-p[1])>0; 42 } 43 44 int top; 45 void graham() { 46 for(int i=2;i<=n;i++) if(p[i]<p[1]) swap(p[i],p[1]); 47 sort(p+2,p+n+1,cmp); 48 q[++top]=p[1]; q[++top]=p[2]; 49 for(int i=3;i<=n;i++) { 50 while(top>1&&cross(q[top]-q[top-1],p[i]-q[top-1])<eps) top--; 51 q[++top]=p[i]; 52 } 53 } 54 55 db RC() { 56 q[top+1]=q[1]; 57 int now=2; 58 db res=0; 59 for(int i=1;i<=top;i++) { 60 while(cross(q[i+1]-q[i],q[now]-q[i])<cross(q[i+1]-q[i],q[now+1]-q[i])) { 61 now++; if(now==top+1) now=1; 62 } 63 res=max(res,length(q[now]-q[i])); 64 } 65 return res; 66 } 67 68 int main() { 69 read(n); 70 for(int i=1;i<=n;i++) { read(p[i].x); read(p[i].y); } 71 graham(); 72 printf("%d\n",(int)RC()); 73 return 0; 74 }
