BZOJ3680: 吊打XXX

模拟退火裸题，爆了n发就是随机wa一个点。

#include <bits/stdc++.h>
using namespace std;
int x[1010], y[1010], w[1010];
double ansx, ansy, ans;
inline double R() {
    return (double)rand() / RAND_MAX;
}
inline double calc(int n, double xx, double yy) {
    double ret = 0; 
    for(int i = 1; i <= n; ++ i) {
        double nx = xx - x[i], ny = yy - y[i];
        ret += (double)sqrt(nx * nx + ny * ny) * w[i];
    } if(ret < ans) {
        ans = ret, ansx = xx, ansy = yy;
    } return ret;
}
inline void Do(int n) {
    double tem = 1e5, X = ansx, Y = ansy;
    while(tem > 1e-4) {
        double nx = X + tem * (R() - 0.5);
        double ny = Y + tem * (R() - 0.5);
        double delta = calc(n, nx, ny) - calc(n, X, Y);
        if(exp(-delta / tem) > R()) {
            X = nx, Y = ny;
        }
        tem = tem * 0.97;
    } for(int i = 1; i <= 1000; ++ i) {
        double nx = ansx + tem * (R() - 0.5);
        double ny = ansy + tem * (R() - 0.5);
        calc(n, nx, ny);
    }
}
int main() {
    srand(time(0));
    int n; scanf("%d",&n);
    for(int i = 1; i <= n; ++ i) {
        scanf("%d%d%d", &x[i], &y[i], &w[i]);
        ansx += x[i], ansy = y[i];
    } ansx /= n, ansy /= n;
    ans = calc(n, ansx, ansy);
    for(int i = 1; i <= 100; ++ i) {
        Do(n); 
    }
    printf("%.3lf %.3lf
", ansx, ansy);
}