BZOJ 1337 最小圆覆盖 随机增量法

题目大意：求最小圆覆盖

我又写了一遍233

尼玛上一遍居然忘记random_shuffle了= =

#include <cmath>#include <cstdio>#include <cstring>#include <iomanip>#include <iostream>#include <algorithm>#define M 100100#define EPS 1e-7using namespace std;struct Point{double x,y;Point() {}Point(double _,double __):x(_),y(__) {}friend istream& operator >> (istream &_,Point &p){scanf("%lf%lf",&p.x,&p.y);return _;}friend Point operator + (const Point &p1,const Point &p2){return Point(p1.x+p2.x,p1.y+p2.y);}friend Point operator - (const Point &p1,const Point &p2){return Point(p1.x-p2.x,p1.y-p2.y);}friend double operator * (const Point &p1,const Point &p2){return p1.x*p2.y-p1.y*p2.x;}friend Point operator * (const Point &p1,double rate){return Point(p1.x*rate,p1.y*rate);}friend double Distance(const Point &p1,const Point &p2){return sqrt( (p1.x-p2.x)*(p1.x-p2.x) + (p1.y-p2.y)*(p1.y-p2.y) ) ;}friend Point Rotate(const Point &p){return Point(-p.y,p.x);}}points[M];struct Line{Point p,v;Line() {}Line(const Point &_,const Point &__):p(_),v(__) {}friend Point Get_Intersection(const Line &l1,const Line &l2){Point u=l1.p-l2.p;double temp=(l2.v*u)/(l1.v*l2.v);return l1.p+l1.v*temp;}};struct Circle{Point o;double r;Circle() {}Circle(const Point &_,double __):o(_),r(__) {}bool In_Circle(const Point &p){return Distance(p,o) < r + EPS ;}}ans;int n;int main(){int i,j,k;srand(19980402);cin>>n;for(i=1;i<=n;i++)cin>>points[i];random_shuffle(points+1,points+n+1);for(i=1;i<=n;i++){if(!ans.In_Circle(points[i])){ans=Circle(points[i],0);for(j=1;j<i;j++)if(!ans.In_Circle(points[j])){ans=Circle((points[i]+points[j])*0.5,Distance(points[i],points[j])*0.5);for(k=1;k<j;k++)if(!ans.In_Circle(points[k])){Line l1=Line((points[i]+points[j])*0.5,Rotate(points[i]-points[j]));Line l2=Line((points[i]+points[k])*0.5,Rotate(points[i]-points[k]));Point O=Get_Intersection(l1,l2);ans=Circle(O,Distance(points[i],O));}}}}cout<<fixed<<setprecision(3)<<ans.r<<endl;return 0;}