POJ 2420 模拟退火

 1 #include <iomanip>
 2 struct Point { double x, y; };
 3 
 4 const double eps = 1e-8;        //搜索条件阀值
 5 const double T = 100;        //初始温度
 6 const double delta = 0.98;    //温度下降速度
 7 int dx[4] = { 1,-1,0,0 };
 8 int dy[4] = { 0,0,1,-1 };
 9 int n;
10 Point p[MAXN];
11 
12 double sqr(double x) {
13     return x * x;
14 }
15 
16 double dist(Point a, Point b) {
17     return sqrt(sqr(a.x - b.x) + sqr(a.y - b.y));
18 }
19 
20 double sum(Point point) {
21     double res = 0;
22     rep(i, 0, n) res += dist(point, p[i]);
23     return res;
24 }
25 
26 int main() {
27     ios::sync_with_stdio(false), cin.tie(0);
28     cin >> n;
29     rep(i, 0, n) cin >> p[i].x >> p[i].y;
30     Point s = p[0];        //随机初始化一个点开始搜索
31     double t = T;        //初始化温度
32     double ans = INF;
33     while (t > eps) {
34         int fg = 1;
35         while (fg) {
36             fg = 0;
37             rep(i, 0, 4) {
38                 Point point = Point{ s.x + dx[i],s.y + dy[i] };
39                 double t = sum(point);
40                 if (ans > t) {
41                     ans = t;
42                     s = point;
43                     fg = 1;
44                 }
45             }
46         }
47         t *= delta;
48     }
49     cout << std::fixed << setprecision(0) << ans << endl;
50     return 0;
51 }