POJ 2420 A Star not a Tree? (模拟退火)

题意：给出平面坐标内的一些点，要求你在坐标平面内找到一点使所有点到该点的距离和最小，输出这个距离

分析：模拟退火，在误差范围内找到近似答案

#include<cstring>
#include<string>
#include<iostream>
#include<queue>
#include<cstdio>
#include<algorithm>
#include<map>
#include<cstdlib>
#include<cmath>
#include<vector>
//#pragma comment(linker, "/STACK:1024000000,1024000000");

using namespace std;

#define INF 0x3f3f3f3f
#define eps 1e-5
#define delte 0.98

struct node
{
double x,y;
} p[105];

int n;
int dir[][5]= {{0,1},{0,-1},{1,0},{-1,0}};

double dis(node a,node b)
{
return sqrt( (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y) );
}

double getsum(node k)
{
double ans=0;
for(int i=0; i<n; i++)
{
ans+=dis(k,p[i]);
}
return ans;
}

double solve()
{
node temp;
temp.x=temp.y=0;
double ans=getsum(temp);
double t=100;
while(t>eps)
{
int flag=1;
while(flag)
{
flag=0;
for(int i=0; i<4; i++)
{
node k=temp;
k.x+=dir[i][0]*t;
k.y+=dir[i][1]*t;
double len=getsum(k);
if(len<ans)
{
ans=len;
temp=k;
flag=1;
}
}
}
t*=delte;
}
return ans;
}

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