bzoj3680 吊打XXX 爬山算法

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#define N 10005
using namespace std;

int n; double ans,ansx,ansy,x
,y
,z
;
double dist(double x1,double y1,double x2,double y2){
return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}
double calc(double u,double v){
double tmp=0; int i;
for (i=1; i<=n; i++) tmp+=dist(x[i],y[i],u,v)*z[i];
if (tmp<ans){ ans=tmp; ansx=u; ansy=v; } return tmp;
}
double getr(){ return (double)(rand()%20000)/20000; }
int main(){
srand(20160309); scanf("%d",&n); int i;
for (i=1; i<=n; i++){
scanf("%lf%lf%lf",&x[i],&y[i],&z[i]);
ansx+=x[i]; ansy+=y[i];
}
ansx/=n; ansy/=n; ans=calc(ansx,ansy);
double sx=ansx,sy=ansy,u,v,t=1e5;
for (; t>1e-3; t*=0.98){
u=sx+t*(getr()*2-1); v=sy+t*(getr()*2-1);
if (calc(u,v)<calc(sx,sy)){ sx=u; sy=v; }
}
printf("%.3f %.3f\n",ansx,ansy);
return 0;
}