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 10050using 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;}