bzoj3680吊打GTY

题意：http://www.lydsy.com/JudgeOnline/problem.php?id=3680

sol  ：吊打出题人（逃~

　　　puts("nan")

　　　出题人题解：http://bakser.blog.163.com/blog/static/23589413220147161124294/

　　　数学&物理结合QAQ，喜sang闻xin乐bing见kuang

　　　引入一下广义费马点：http://www.matrix67.com/blog/archives/422

　　　然后爬山or退火乱搞即可

#include<iostream>
#include<cstdio>
#include<cmath>
#define eps 0.00000001
using namespace std;
const int Mx=10010;
double x,y,tmp=1000,ansx,ansy;
struct Node { double x,y; int w; } str[Mx];
double dis(double x,double y,Node z)
{
    return sqrt((x-z.x)*(x-z.x)+(y-z.y)*(y-z.y));
}
int main()
{
    int n; scanf("%d",&n);
    for(int i=1;i<=n;i++) scanf("%lf%lf%d",&str[i].x,&str[i].y,&str[i].w);
    for(int i=1;i<=n;i++)
        ansx+=str[i].x*str[i].w,ansy+=str[i].y*str[i].w;
    ansx/=n;ansy/=n;
    while(tmp>eps)
    {
        x=y=0;
        for(int i=1;i<=n;i++)
        {
            x+=(str[i].x-ansx)*str[i].w/dis(ansx,ansy,str[i]);
            y+=(str[i].y-ansy)*str[i].w/dis(ansx,ansy,str[i]);
        }
        ansx+=x*tmp,ansy+=y*tmp;
        if(tmp>0.5) tmp*=0.5;
        else tmp*=0.97;
    }
    printf("%.3lf %.3lf
",ansx,ansy);
    return 0;
}