模擬退火模板

學習博客
題目鏈接
玄學算法。。。一開始不知道調參wa到懷疑人生
後來嘗試改一下delta竟然過了。。。
這道題正解可以用爬山算法來做，佔坑有空補一下

#pragma GCC optimize(2)
#include<bits/stdc++.h>
using namespace std;
#define ft first
#define sd second
#define all(c) ((c).begin()), ((c).end())
#define mp(a, b) make_pair(a, b)
#define pb(x) push_back(x)
const int maxn = 1e5+5;
typedef long long ll;
const ll mod = 1e9+7;
int Case = 1;
int n, m;
struct node{
    int x, y, z;
}cc[maxn];
int sx, sy;
double resx, resy;
double res = 1e18, t;
const double delta = 0.992;//記得調參
double cal_energy(double x, double y) {//計算能量
    double rt = 0;
    for(int i = 1; i <= n; i++) {
        double deltax = x-cc[i].x, deltay = y-cc[i].y;
        rt += sqrt(deltax*deltax+deltay*deltay)*cc[i].z;
    }
    return rt;
}
void simulate_anneal() {//模擬退火
    double x = resx, y = resy;
    t = 2000;
    while(t > 1e-14) {
        double X = x+((rand()<<1)-RAND_MAX)*t;
        double Y = y+((rand()<<1)-RAND_MAX)*t;
        double now = cal_energy(X, Y);
        double new_delta = now-res;
        if(new_delta < 0) {
            x = X;y = Y;
            resx = x;resy = y;res = now;
        }
        else if(exp(-new_delta/t)*RAND_MAX>rand())x = X, y = Y;
        t *= delta;
    }
}
void solve() {
    cin>>n;
    for(int i = 1; i <= n; i++) 
        cin>>cc[i].x>>cc[i].y>>cc[i].z, sx+=cc[i].x, sy+=cc[i].y;
    resx = 1.0*sx/n;resy = 1.0*sy/n;
    //多調用幾次更精確。。
    simulate_anneal();
    simulate_anneal();
    simulate_anneal();
    printf("%.3f %.3f\n", resx, resy);
    return;
}
int main() {
    srand(rand());srand(rand());srand(rand());
    ios::sync_with_stdio(false);cin.tie(0);std::cout.tie(0);
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    //freopen("out.txt","w",stdout);
#endif
    //scanf("%d", &Case);
    while(Case--){
        solve();
    }
    return 0;
}