3680: 吊打XXX

3680: 吊打XXX

链接

思路：

　　模拟退火。

代码：

跑的特别慢。。。

 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<cctype>
 #include<cmath>

 using namespace std;

 const int N = ;
 struct Node{
     double x,y,w;
 }d[N],ans;
 int n;
 double minans = 1e18;

 double dis(Node a,Node b) {
     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
 }
 double check(Node p) {
     double ret = ;
     for (int i=; i<=n; ++i)
         ret += d[i].w*dis(p,d[i]);
     if (ret < minans)
         ans = p,minans = ret;
     return ret;
 }
 double Rand() {
     return rand()%/1000.0;
 }
 void SA() {
     double T = ;
     Node now = ans;
     while (T > 0.001) {
         Node nxt;
         nxt.x = now.x+T*(Rand()*2.0-1.0);
         nxt.y = now.y+T*(Rand()*2.0-1.0);
         double Delta = check(now)-check(nxt);
         if (Delta >  || exp(Delta/T)>Rand()) now = nxt;
         T *= 0.993;
     }
     for (int i=; i<=; ++i) {
         Node nxt;
         nxt.x = ans.x+T*(Rand()*2.0-1.0);
         nxt.y = ans.y+T*(Rand()*2.0-1.0);
         check(nxt);
     }
 }
 int main() {
     srand();
     scanf("%d",&n);
     ans.x = ans.y = ;
     for (int i=; i<=n; ++i) {
         scanf("%lf%lf%lf",&d[i].x,&d[i].y,&d[i].w);
         ans.x += d[i].x;
         ans.y += d[i].y;
     }
     ans.x /= (double)n;
     ans.y /= (double)n;
     SA();
     printf("%.3lf %.3lf",ans.x,ans.y);
     return ;
 }