梯度下降&模拟退火

#include<cstdio>
#include<cmath>
#include<cstdlib>
#define rep(i,a,b) for(int i=a;i<=b;++i)
using namespace std;
const double eps=1e-8;
const double T_min=1e-8;
const double PI=acos(-1.0);
const double step=0.99;
const int MAXN=10010;
double tot;
int n;
struct Point
{
    double x,y,w;
    Point() {}
    Point(double xx,double yy) {x=xx;y=yy;}
    Point operator -(const Point &b)const
    {
        return Point(x-b.x,y-b.y);
    }
    Point operator +(const Point &b)const
    {
        return Point(x+b.x,y+b.y);
    }
    double operator *(const Point &b)const
    {
        return x*b.x+y*b.y;
    }

}p[MAXN];
Point now,ans;
double dist(Point a,Point b)
{
    return sqrt((a-b)*(a-b));
}
double random01()
{
    return (rand()%1000+1)/1000.0;
}
double fx(Point x)
{
    double res=0.0;
    rep(i,1,n) res+=dist(x,p[i])*p[i].w;
    if(res<tot) {tot=res;ans=x;}
    return res;
}
int main()
{
    srand(2333);
    //freopen("in.txt","r",stdin);
    int a,b,w,dif;
    tot=1e18;
    scanf("%d",&n);
    rep(i,1,n)
    {
        scanf("%lf%lf%lf",&p[i].x,&p[i].y,&p[i].w);
        now=now+p[i];
    }
    now.x/=n;now.y/=n;
    double T=100000.0,alpha;
    while(T>T_min)
    {
        alpha=2.0*PI*random01();
        Point tmp(now.x+T*cos(alpha),now.y+T*sin(alpha));
        dif=fx(now)-fx(tmp);
        if(dif>=0||exp(dif/T)>random01()) now=tmp;
        T*=step;
    }
    T=0.001;
    rep(i,1,1000)
    {
        alpha=2.0*PI*random01();
        Point tmp(ans.x+ T*cos(alpha)*random01(),ans.y+T*sin(alpha)*random01());
        fx(tmp);
    }
    printf("%.3f %.3f\n",ans.x,ans.y);
    return 0;
}