POJ 2420 A Star not a Tree?(模拟退火)

题目链接

居然1Y了，以前写的模拟退火很靠谱啊。

#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <iostream>
using namespace std;
struct point
{
    double x,y;
}p[201];
int n;
int a[4] = {0,0,-1,1};
int b[4] = {1,-1,0,0};
double dis(double x1,double y1,double x2,double y2)
{
    return sqrt((x1-x2)*(x1-x2)+(y2-y1)*(y2-y1));
}
double fun(double x,double y)
{
    double ans = 0;
    int i;
    for(i = 0;i < n;i ++)
    {
        ans += dis(p[i].x,p[i].y,x,y);
    }
    return ans;
}
int main()
{
    int T,i,key,num,j,k;
    double tx,ty,ans,d,x,y;
    srand(time(NULL));
    scanf("%d",&n);
    for(i = 0;i < n;i ++)
    {
        scanf("%lf%lf",&p[i].x,&p[i].y);
    }
    key = 5;
    ans = 100000000;
    num = 200;
    x = p[0].x;
    y = p[0].y;
    T = 40;
    while(T--)
    {
        for(i = 1;i <= num;i ++)
        {
            for(j = 0;j < 4;j ++)
            {
                k = rand()%key;
                tx = x + k*a[j]*T;
                ty = y + k*b[j]*T;
                if(tx >= 0&&tx <= 10000&&ty >= 0&&ty <= 10000)
                {
                    d = fun(tx,ty);
                    if(ans > d)
                    {
                        ans = d;
                        x = tx;
                        y = ty;
                    }
                }
            }
        }
    }
    printf("%.f
",ans);
    return 0;
}