UVA 10228 - Star not a Tree?(模拟退火)

UVA 10228 - Star not a Tree?

题目链接

题意：给定一些点，费马点(到这些点距离和最短)，输出距离和

思路：模拟退火去搞，初始温度1W步，降温系数设为0.83，然后每次找周围4个方向，做10次保证答案准确

代码：

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

const int d[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};

const int N = 105;
const double eps = 1e-3;

int t, n;

struct Point {
double x, y, d;
Point() {}
Point(double a, double b) {
x = a; y = b;
}
} p
;

double getdis(Point P) {
double ans = 0;
for (int i = 0; i < n; i++) {
double dx = p[i].x - P.x;
double dy = p[i].y - P.y;
ans += sqrt(dx * dx + dy * dy);
}
return ans;
}

double gao() {
int cnt = 10;
double ans = 1e20, r = 0.83;
srand(time(NULL));
while (cnt--) {
double step = 1e4;
Point now = Point(rand() % 10001, rand() % 10001);
now.d = getdis(now);
while (step > eps) {
Point next;
for (int i = 0; i < 4; i++) {
next = Point(now.x + step * d[i][0], now.y + step * d[i][1]);
next.d = getdis(next);
if (next.d < now.d)
now = next;
}
step *= r;
ans = min(ans, now.d);
}
}
return ans;
}

int main() {
scanf("%d", &t);
while (t--) {
scanf("%d", &n);
for (int i = 0; i < n; i++)
scanf("%lf %lf", &p[i].x, &p[i].y);
printf("%.0lf\n", gao());
if (t) printf("\n");
}
return 0;
}