bzoj 3680 吊打xxx 模拟退火

第一道模拟退火

重心嘛，就是要找到一个点，使其到所有点距离*该点权值和最小

思路：初始化一个T，mint,当T大于mint时，每次随机一个解，如果解比当前解优，直接转移，否则，以某概率（与T正相关）转移，并不断降温，最后向四周爬山

感觉思路比较清晰，但好多细节不太明白，比如初始化的T，mint，以及退火的速度，前后改了几十遍吧。还是要多做题，找感觉......

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
#define N 10050
using namespace std;
int n;
double minn=0x3f3f3f3f3f3f3f3fll;
struct point{
	double x,y,g;
}p[N],ans;
double sqr(double x){return x*x;}
double dis(point a,point b){return sqrt(sqr(a.x-b.x)+sqr(a.y-b.y));}
double Rand(){return (rand()%1000)/1000.0;}
double judge(point pp){
	double ret=0;
	for(int i=1;i<=n;i++)
		ret+=p[i].g*dis(p[i],pp);
	if(ret<minn){minn=ret;ans=pp;}
	return ret;
}
void work(){
	double T=1000000;
	point now=ans;
	while(T>0.001){
		point nxt;
		nxt.x=now.x+T*(Rand()*2-1);
		nxt.y=now.y+T*(Rand()*2-1);
		double dE= judge(now)-judge(nxt);
		if((dE>0)||(exp(dE/T)>Rand())) now=nxt;
		T*=0.97;
	}
	double nouse;
	for(int i=1;i<=1000;i++){
		point nxt;
		nxt.x=ans.x+T*(Rand()*2-1);
		nxt.y=ans.y+T*(Rand()*2-1);
		nouse=judge(nxt);
	}
}
int main(){
	srand(20001101);
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%lf%lf%lf",&p[i].x,&p[i].y,&p[i].g);
		ans.x+=p[i].x; ans.y+=p[i].y;
	}
	ans.x/=n; ans.y/=n;
	work();
	printf("%0.3lf %0.3lf\n",ans.x,ans.y);
	return 0;
}