洛谷 P1337 [JSOI2004]平衡点 / 吊打XXX

平衡点 / 吊打XXX

模拟退火入坑题

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Code:

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <cstdlib>
using namespace std;
//Mystery_Sky
//
#define M 1000100
#define INF 0x3f3f3f3f
struct node {
    int x, y, w;
}point[M];
int n;
double Ans_x, Ans_y;
double t, Ans = 1e18;
int sum_x, sum_y;
const double delta = 0.993;

inline double dist(double x, double y)
{
    double sum = 0;
    for(int i = 1; i <= n; i++) {
        double dx = point[i].x - x;
        double dy = point[i].y - y;
        sum += sqrt(dx * dx + dy * dy) * point[i].w;
    }
    return sum;
}

inline void SA()
{
    double x, y;
    x = Ans_x, y = Ans_y;
    t = 2000;
    while(t > 1e-14) {
        double new_x = x + ((rand()<<1) - RAND_MAX) * t;
        double new_y = y + ((rand()<<1) - RAND_MAX) * t;
        double new_ans = dist(new_x, new_y);
        double DE = new_ans - Ans;
        if(DE < 0) {
            Ans_x = x = new_x, Ans_y = y = new_y;
            Ans = new_ans;
        }
        else if(exp(-DE/t) * RAND_MAX > rand()) x = new_x, y = new_y;
        t *= delta;
    }
}

int main() {
    srand(19260817);
    srand(rand());
    srand(rand());
    scanf("%d", &n);
    for(int i = 1; i <= n; i++) {
        scanf("%d%d%d", &point[i].x, &point[i].y, &point[i].w);
        sum_x += point[i].x;
        sum_y += point[i].y;
    }
    Ans_x = (double) sum_x/n;
    Ans_y = (double) sum_y/n;
    SA();
    SA();
    SA();
    printf("%.3lf %.3lf\n", Ans_x, Ans_y);
    return 0;
}