BZOJ3680: 吊打XXX
模拟退火裸题，爆了n发就是随机wa一个点。
1 #include <bits/stdc++.h> 2 using namespace std; 3 int x[1010], y[1010], w[1010]; 4 double ansx, ansy, ans; 5 inline double R() { 6 return (double)rand() / RAND_MAX; 7 } 8 inline double calc(int n, double xx, double yy) { 9 double ret = 0; 10 for(int i = 1; i <= n; ++ i) { 11 double nx = xx - x[i], ny = yy - y[i]; 12 ret += (double)sqrt(nx * nx + ny * ny) * w[i]; 13 } if(ret < ans) { 14 ans = ret, ansx = xx, ansy = yy; 15 } return ret; 16 } 17 inline void Do(int n) { 18 double tem = 1e5, X = ansx, Y = ansy; 19 while(tem > 1e-4) { 20 double nx = X + tem * (R() - 0.5); 21 double ny = Y + tem * (R() - 0.5); 22 double delta = calc(n, nx, ny) - calc(n, X, Y); 23 if(exp(-delta / tem) > R()) { 24 X = nx, Y = ny; 25 } 26 tem = tem * 0.97; 27 } for(int i = 1; i <= 1000; ++ i) { 28 double nx = ansx + tem * (R() - 0.5); 29 double ny = ansy + tem * (R() - 0.5); 30 calc(n, nx, ny); 31 } 32 } 33 int main() { 34 srand(time(0)); 35 int n; scanf("%d",&n); 36 for(int i = 1; i <= n; ++ i) { 37 scanf("%d%d%d", &x[i], &y[i], &w[i]); 38 ansx += x[i], ansy = y[i]; 39 } ansx /= n, ansy /= n; 40 ans = calc(n, ansx, ansy); 41 for(int i = 1; i <= 100; ++ i) { 42 Do(n); 43 } 44 printf("%.3lf %.3lf\n", ansx, ansy); 45 }
