POJ - 2420

模拟退火逼近

#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <cmath>

using namespace std;

struct point
{
   double x, y;
}sta[110];

double getdis(point a, point b)
{
    return sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y));
}

double sumdis(point cir, int n)
{
    double ans = 0;
    for( int i = 0; i < n; i++)
        ans += getdis(cir, sta[i]);
    return ans;
}
point fermentpoint(int n)
{
    point  v, u;
    u.x = 0, u.y = 0;
    double step = 100.0;
    double dist = sumdis(u, n);
    int i, j, k;
    while(step > 0.2)
    {
        bool ok = true;
        while(ok)
        {
            ok =false;
            for( int i = -1; i <= 1; i++)
                for( int j = -1; j <= 1; j++)
            {
                v.x = u.x + step*i;
                v.y = u.y + step*j;
                double temp = sumdis(v, n);
                if(temp < dist)
                {
                    dist = temp;
                    ok = true;
                    u = v;
                }
            }
        }
        step /= 2.0;
    }

    return u;
}

int main()
{
    int n;
    while(scanf("%d",&n) != EOF)
    {
        point u;
        double tot = 0;
        for( int i =0; i < n; i++)
          scanf("%lf%lf",&sta[i].x, &sta[i].y);
       point res = fermentpoint(n);
       printf("%d\n",(int)(sumdis(res,n)+0.5)*100/100);
    }
    return 0;
}