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[N];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;}