POJ-2420 A Star not a Tree?

題意: 給定n個點, 找到一個點p. 使得p到所有點的距離之和最小.
分析: 模擬退火隨機產生圓心座標, 跑一遍模擬退火就行, 這題n的範圍是100, 莫名其妙re, 開1000就ac了.
程式碼:

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <iostream>
using namespace std;
 


const int MAXN = 1111;

const double eps = 1e-8;
const double pi = acos(-1);
const double inf = 0x3f3f3f3f;
struct Point {
  double x, y;
  Point() {}
  Point(double _x, double _y) {
    x = _x;
    y = _y;
  }
  double distance(Point b) { return hypot(x - b.x, y - b.y); }
};
Point p[MAXN];
int n;
Point ans;
 

double Rand() { return (double)rand() / RAND_MAX; }

double getdis(Point b) {
  double res = 0;
  for (int i = 0; i < n; i++) {
    res += b.distance(p[i]);
  }
  return res;
}
int main() {
  srand(0);
  while (scanf("%d", &n) != EOF) {
    ans.x = 0, ans.y = 0;
    for (int i = 0; i < n; i++) {
 

      scanf("%lf%lf", &p[i].x, &p[i].y);
      ans.x += p[i].x;
      ans.y += p[i].y;
    }
    ans.x /= n;
    ans.y /= n;
    double t = 100000;
    double res = getdis(ans);
    Point nxt;
    while (t > eps) {
      nxt.x = ans.x + t * (Rand() * 2 - 1);
      nxt.y = ans.y + t * (Rand() * 2 - 1);
      double dis = getdis(nxt);
      if (res > dis) {
        res = dis;
        ans = nxt;
      }
      t *= 0.97;
    }
    printf("%.0f", res);
  }
  return 0;
}