POJ2420——A Star not a Tree?

题目链接：http://poj.org/problem?id=2420

A Star not a Tree?

题目大意：求费马点！！！模拟退火即可......

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#define eps 1e-9
#define INF 0xfffffff
using namespace std;

int n;
int dx[]={-1,-1,-1,0,1,1,1,0},dy[]={1,0,-1,-1,-1,0,1,1};
double ans,t;

struct point
{
    double x,y;
}p[110];

double dis(double x1,double y1,double x2,double y2)
{
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

double fun2(double x,double y)
{
    double sum=0;
    for(int i=0;i<n;i++)
        sum+=dis(x,y,p[i].x,p[i].y);
    return sum;
}

void fun(double x,double y)
{
    t=1;
    ans=fun2(x,y);
    double xx,yy,sum,tmpx,tmpy;
    while(t>eps)
    {
        int flag=1;
        while(flag)
        {
            flag=0;
            for(int i=0;i<8;i++)
            {
                xx=x+dx[i]*t;
                yy=y+dy[i]*t;
                sum=fun2(xx,yy);
                if(ans>sum)
                {
                    ans=sum;
                    tmpx=xx;
                    tmpy=yy;
                    flag=1;
                }
            }
            x=tmpx;
            y=tmpy;
        }
        t*=0.99;
    }
    printf("%.lf\n",ans);
}

int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        int i;
        for(i=0;i<n;i++)
            scanf("%lf%lf",&p[i].x,&p[i].y);
        fun(0,0);
    }
    return 0;
}