ZOJ 2928 模拟退火 求三维费马点

#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<map>
#include<queue>
#include<cmath>
using namespace std;
#define eps 1e-12
#define N 110
#define M 2001000
#define ll long long
#define inf 0x3f3f3f3f

int n,cnt;
struct P
{
double x,y,z;
P(){}
P(double _x,double _y,double _z)
:x(_x),y(_y),z(_z){}
double len()
{
return sqrt(x*x+y*y+z*z);
}
P operator+(const P p)
{
return P(x+p.x,y+p.y,z+p.z);
}
P operator-(const P p)
{
return P(x-p.x,y-p.y,z-p.z);
}
P operator*(double c)
{
return P(x*c,y*c,z*c);
}

}p
,dir[30];
int dblcmp(double x)
{
return (x>eps)-(x<-eps);
}
void init()
{
for(int i=-1;i<=1;i++)
for(int j=-1;j<=1;j++)
for(int k=-1;k<=1;k++)
dir[cnt++] = P(i,j,k);

}
void solve()
{
double step = 100;
double mi = 1e10;
P ans = P(0,0,0),now,nxt;
for(int j=0;j<n;j++)
ans = ans+p[j];
ans = ans * (1.0/n);
while(step>eps)
{
nxt = ans;
for(int i=0;i<cnt;i++)
{
now = ans+dir[i]*step;
double tmp = 0;
for(int j=0;j<n;j++)
tmp += (now-p[j]).len();
if(dblcmp(tmp-mi)<0)
{
mi = tmp;
nxt = now;
}
}
ans = nxt;
step *= 0.993;

}
printf("%.3lf %.3lf %.3lf\n",ans.x,ans.y,ans.z);
}
int main()
{
init();
while(scanf("%d",&n)!=EOF)
{
for(int i=0;i<n;i++)
scanf("%lf%lf%lf",&p[i].x,&p[i].y,&p[i].z);

solve();

}
return 0;
}