洛谷P1337 [JSOI2004]平衡点 / 吊打XXX 

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 typedef double db;
 5 const int N=1e3+5;
 6 db ansx,ansy,answ;
 7 int n; 
 8 struct point{
 9     int x,y,w;
10 }p[N];
11 
12 ll read()
13 {
14     ll x=0,f=1;char ch=getchar();
15     while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
16     while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}
17     return x*f;
18 }
19 db f(db x,db y)
20 {
21     db sum=0;
22     for(int i=1;i<=n;i++)
23     {
24         db delx=x-p[i].x;
25         db dely=y-p[i].y;
26         sum+=1.0*sqrt(delx*delx+dely*dely)*p[i].w;
27     }
28     return sum;
29 }
30 void mnth()
31 {
32     for(db T=3000;T>1e-15;T*=0.996)
33     {
34         db nowx=ansx+(2*rand()-RAND_MAX)*T;
35         db nowy=ansy+(2*rand()-RAND_MAX)*T;
36         db delt=f(nowx,nowy)-f(ansx,ansy);
37         if(delt<0)ansx=nowx,ansy=nowy;
38         else if(exp(-delt/T)*RAND_MAX>rand())ansx=nowx,ansy=nowy;
39     }
40 }
41 int main()
42 {
43     n=read();
44     for(int i=1;i<=n;i++)
45     {
46         p[i].x=read();p[i].y=read();p[i].w=read();
47         ansx+=p[i].x;ansy+=p[i].y;    
48     }
49     ansx/=n;ansy/=n;
50     mnth();
51     mnth();
52     printf("%.3lf %.3lf\n",ansx,ansy);
53     return 0;
54 }

 

posted @ 2022-04-03 15:50  matt-11  阅读(49)  评论(0)    收藏  举报