@[LHTCFLS](/user/436107) 这样写。
说下错误：
- 直接 `rand() / RAND_MAX` 不会是浮点数，会变成 $0$。这是主要问题。
- 卡时。
- 微调一下参数，要不然卡时卡不满。
不知道是怎么回事，我交了 3 发只过了 2 发，应该是退火内部哪里写错了。
```cpp
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define inf 0x3f
#define inf_db 127
#define ls id << 1
#define rs id << 1 | 1
#define re register
#define endl '\n'
typedef pair <int,int> pii;
const int MAXN = 1e3 + 10;
int n,x[MAXN],y[MAXN],w[MAXN];
double ansx,ansy,dis;
double calc(double nx,double ny)
{
double res = 0;
for(int i = 1;i <= n;++i)
{
double dx = x[i] - nx,dy = y[i] - ny;
res += sqrt(dx * dx + dy * dy) * w[i];
}
if(res < dis) dis = res,ansx = nx,ansy = ny;
return res;
}
void SimulateAnneal()
{
double t = 3000;
double nowx = ansx,nowy = ansy;
while(t > 1e-15)
{
double nxtx = nowx + t * (rand() * 2 - RAND_MAX);
double nxty = nowy + t * (rand() * 2 - RAND_MAX);
double delta = calc(nxtx,nxty) - calc(nowx, nowy);
if(delta < 0 || exp(-delta / t) * RAND_MAX > rand()) nowx = nxtx,nowy = nxty;
t *= 0.99522;
}
}
signed main()
{
srand(time(0));
cin >> n;
for(int i = 1;i <= n;i++)
{
cin >> x[i] >> y[i] >> w[i];
ansx += x[i],ansy += y[i];
}
ansx /= n,ansy /= n,dis = calc(ansx,ansy);
while ((double)clock() / CLOCKS_PER_SEC < 0.97) SimulateAnneal();
printf("%.3lf %.3lf",ansx,ansy);
return 0;
}
```
by FastFourierTransform @ 2023-10-15 17:46:46
@[FastFourierTransform](/user/806728) 谢谢！
by Creeper_l @ 2023-10-15 18:51:35