bzoj2823[AHOI2012]信号塔

来源：互联网发布：淘宝清洗订单会降权吗编辑：程序博客网时间：2024/05/18 03:43

随机增量法求最小覆盖圆，主要就是圆心坐标神烦，后来看到了ACdreamer的一个简洁版本，虽然还没明白是为什么但是比窝那个短多了

#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<cstdlib>#include<algorithm>#include<iomanip>#define LL long long#define fo(i,a,b) for(int i=a;i<=b;i++)using namespace std;#define N 1000005#define eps 1e-8struct P{double x,y;}d[N];int n;double dis(P a,P b){return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}P get(P A,P B,P C){P t;      double a1=B.x-A.x,b1=B.y-A.y,c1=(a1*a1+b1*b1)/2;      double a2=C.x-A.x,b2=C.y-A.y,c2=(a2*a2+b2*b2)/2;      double d=a1*b2-a2*b1;      t.x=A.x+(c1*b2-c2*b1)/d;      t.y=A.y+(a1*c2-a2*c1)/d;      return t;}  P get(P a,P b){return (P){(a.x+b.x)/2,(a.y+b.y)/2};}int main(){scanf("%d",&n);fo(i,1,n) scanf("%lf%lf",&d[i].x,&d[i].y);P t=d[1];double r=0.0;fo(i,1,n){if (dis(d[i],t)<=r+eps) continue;t=d[i];r=0;fo(j,1,i-1){if (dis(d[j],t)<=r+eps) continue;t=get(d[i],d[j]);r=dis(d[j],t);fo(k,1,j-1){if (dis(d[k],t)<=r+eps) continue;t=get(d[i],d[j],d[k]);r=dis(d[k],t);}}}printf("%.2lf %.2lf %.2lf\n",t.x,t.y,r);return 0;}

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