poj 2349 Arctic Network

#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstdio>
using namespace std;
#define maxn 600
int par[maxn];
int pos;
int n,cnt,m;
double len;
double tt[maxn];//存选取的道路
struct node
{
    int x;
    int y;
    double w;
};
node e[maxn * (maxn - 1) / 2];
int cmp(const node &a , const node &b)
{
    return a.w < b.w;
};
struct p
{
    int x;
    int y;
} po[maxn];
void init()
{
    for(int i = 0; i <= n+5; i++)
        par[i] = i;
    pos = 0;
    len = 0.0;
    cnt = 0;
}
int Find(int x)
{
    int k,j,r;
    r = x;
    while(par[r] != r)
        r = par[r];
    k = x;
    while(k != r)
    {
        j = par[k];
        par[k] = r;
        k = j;
    }
    return r;
}
int Merge(int x,int y)
{
    int a = Find(x);
    int b = Find(y);
    if(a != b)
    {
        par[a] = par[b];
        return 1;
    }
    return 0;
}
void input()
{
    int u,v;
    for(int i = 1; i <= n; i++)
        scanf("%d%d",&po[i].x,&po[i].y);
}

void make()
{
    init();
    double dist;
    for(int i = 1; i < n; i++)
    {
        for(int j = i + 1; j <= n; j++)
        {
            dist = (po[i].x - po[j].x) * (po[i].x - po[j].x) + (po[i].y - po[j].y) * (po[i].y - po[j].y);
            e[pos].x = i;
            e[pos].y = j;
            e[pos].w = sqrt(dist);
            pos++;
        }
    }
    sort(e,e+pos,cmp);
    for(int i = 0; i < pos; i++)
    {
        if(Merge(e[i].x,e[i].y))
        {
            tt[cnt] = e[i].w;
            cnt++;
        }
        if(cnt == n - 1)break;
    }
}
int main()
{
    freopen("input.txt","r",stdin);
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d",&m,&n);
        input();
        make();
        printf("%.2lf
",tt[cnt - m]);
    }

    return 0;
}