模拟退火

没时间复习这个了，暂时用来当模板，以后再来写下自己的模板

#include <iostream>  
#include <algorithm>  
#include <cstdlib>  
#include <cmath>  
#include <ctime>  
#include <cstdio>  
using namespace std;  
struct Point  
{  
    double x,y;  
}a[105];  
int n;  
double dis(double x,double y,Point a)  
{  
    return sqrt((x-a.x)*(x-a.x)+(y-a.y)*(y-a.y));  
}  
double Getans(double x,double y)  
{  
    double ans=0.0;  
    for (int i=1;i<=n;i++)  
        ans+=dis(x,y,a[i]);  
    return ans;  
}  
int main()  
{  
    //srand((unsigned)time(0));  
    while (scanf("%d",&n)!=EOF)  
    {  
        double x=0,y=0,t=1e5,ans=1e20;  
        for (int i=1;i<=n;i++)  
        {  
            scanf("%lf%lf",&a[i].x,&a[i].y);  
            x+=a[i].x,y+=a[i].y;  
        }  
        x/=n,y/=n;  
        ans=Getans(x,y);  
        while (t>0.02)  
        {  
            double tx,ty;  
            tx=0,ty=0;  
            for (int i=1;i<=n;i++)  
            {  
                tx+=(a[i].x-x)/dis(x,y,a[i]);  
                ty+=(a[i].y-y)/dis(x,y,a[i]);  
            }  
            double tmp=Getans(x+tx*t,y+ty*t);  
            if (tmp<ans)  
                ans=tmp,x+=tx*t,y+=ty*t;  
            else if (t>(double)(rand()%100000))  
                ans=tmp,x+=tx*t,y+=ty*t;  
            t*=0.9;  
        }  
        printf("%.0f
",ans);  
    }  
    return 0;  
}