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  • BZOJ 1336&1337最小圆覆盖

    思路:
    http://blog.csdn.net/commonc/article/details/52291822
    (照着算法步骤写……)
    已知三点共圆 求圆心的时候 就设一下圆心坐标(x,y) 解个方程就好了

    //By SiriusRen
    #include <cmath>
    #include <cstdio>
    #include <algorithm>
    using namespace std;
    int n;double R,tempx,tempy,tempz,tmpx,tmpy,tmpz;
    struct Point{double x,y;}point[100050],Ans;
    double Sqr(double x){return x*x;}
    double dis(Point a,Point b){return sqrt(Sqr(a.x-b.x)+Sqr(a.y-b.y));}
    bool in_circle(Point x){return dis(Ans,x)<=R;}
    int main(){
        scanf("%d",&n);
        for(int i=1;i<=n;i++)scanf("%lf%lf",&point[i].x,&point[i].y);
        random_shuffle(point+1,point+n);
        for(int i=1;i<=n;i++)if(!in_circle(point[i])){
            Ans.x=point[i].x,Ans.y=point[i].y,R=0;
            for(int j=1;j<i;j++)if(!in_circle(point[j])){
                Ans.x=(point[i].x+point[j].x)/2;
                Ans.y=(point[i].y+point[j].y)/2;
                R=dis(Ans,point[j]);
                for(int k=1;k<j;k++)if(!in_circle(point[k])){
                    tempz=point[j].x-point[i].x;
                    tempx=2*(point[i].y-point[j].y)/tempz;
                    tempy=(Sqr(point[j].x)+Sqr(point[j].y)-Sqr(point[i].x)-Sqr(point[i].y))/tempz;
                    tmpz=point[k].x-point[j].x;
                    tmpx=2*(point[j].y-point[k].y)/tmpz;
                    tmpy=(Sqr(point[k].x)+Sqr(point[k].y)-Sqr(point[j].x)-Sqr(point[j].y))/tmpz;
                    Ans.y=(tmpy-tempy)/(tempx-tmpx);
                    Ans.x=(tempx*Ans.y+tempy)/2;
                    R=dis(Ans,point[j]);
                }
            }
        }
        printf("%f
    %f %f
    ",R,Ans.x,Ans.y);
    }

    这里写图片描述

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  • 原文地址:https://www.cnblogs.com/SiriusRen/p/6532109.html
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