bzoj3680 吊打XXX

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模拟退火。

#include<cstdio>#include<cmath>#include<algorithm>using namespace std;const double tmax=10000,r=0.995,eps=1e-5;const int maxn=10010;int xx[maxn],yy[maxn],w[maxn],n;double cal(double x,double y){    double ret=0;    for (int i=1;i<=n;i++)        ret+=sqrt((x-xx[i])*(x-xx[i])+(y-yy[i])*(y-yy[i]))*w[i];    return ret;}double get(double lim){    return (double)rand()/RAND_MAX*(2*lim)-lim;}int main(){    srand(233);    double x=0,y=0,x1,y1,now,tem;    scanf("%d",&n);    for (int i=1;i<=n;i++) scanf("%d%d%d",&xx[i],&yy[i],&w[i]),x+=xx[i],y+=yy[i];    x/=n;    y/=n;    now=cal(x,y);    for (double t=tmax;t>eps;t*=r)    {        x1=x+get(t);        y1=y+get(t);        tem=cal(x1,y1);        if (tem<now||exp((now-tem)/t)>get(0.5)+0.5)        {            x=x1;            y=y1;            now=tem;        }    }    for (double t=0.1;t>eps;t*=r)    {        x1=x+get(t);        y1=y+get(t);        tem=cal(x1,y1);        if (tem<now)        {            x=x1;            y=y1;            now=tem;        }    }    printf("%.3f %.3f\n",x,y);}

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