uva 10369

数组开小了  还RE了一遍.......  最小生成树    按费用从小到大排。。。

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>

using namespace std;

int n, m, s, p[300000];
struct node
{
    int u,v;
    double len;
    bool operator < (const node &p) const
    {
        return len < p.len;
    }
};
node cc[300000];
int find(int x)
{
    return p[x] == x ? x : (p[x] =find(p[x]));
}
double kk()
{
    int q = 0;
    for(int i = 0; i < s; i++)
        p[i] = i;
    sort(cc, cc+m);
    for(int i = 0; i < m; i++)
    {
        int x = find(cc[i].u);
        int y = find(cc[i].v);
        if(x != y)
        {
            p[x] = y;
            q++;
            if(q == s - n)
                return cc[i].len;
        }
    }
    return 0;
}
int main()
{
    int t;
    double x[510], y[510];
    scanf("%d", &t);
    while(t--)
    {
        m = 0;
        scanf("%d%d", &n, &s);
        for(int i = 0; i < s; i++)
            scanf("%lf%lf", &x[i], &y[i]);
        for(int i = 0; i < s; i++)
            for(int j = i+1; j < s; j++)
            {
                cc[m].u = i, cc[m].v = j;
                double d1 = x[i] - x[j], d2 = y[i] - y[j];
                cc[m++].len = sqrt(d1*d1 + d2*d2);
            }
        printf("%.2lf\n",kk());
    }
    return 0;
}