hdu 1875 最小生成树(kruskal)

/*
题意：中文题

题解：赤裸裸的最小生成树
*/
#include <cstdio>
#include <cmath>
#include <algorithm>

const int MAXN = 109;
const int MAXE = 10009;

struct edge
{
    int u, v;
    double w;
    bool vis;
}E[MAXE];

int set[MAXN];
int N, EN, sum;

void addedge(int u, int v, double w)
{
    E[ EN ].u = u;
    E[ EN ].v = v;
    E[ EN ].w = w;
    E[ EN ].vis = false;
    EN++;
    return ;
}

void init()
{    
    for (int i = 1; i <= N; i++) // 树的标号从1开始
        set[i] = i;
    return ;
}

int find(int x)
{
    while (set[x] != x)
        x = set[x];
    return set[x];
}

bool cmp(edge a, edge b)
{
    return a.w < b.w;
}

double kruskal()
{
    int x, y;
    double ret;
    init();
    sum = 0;
    ret = 0;
    std::sort(E,E+EN,cmp);
    for (int i = 0; i < EN && sum < N - 1; i++)
    {
        x = find( E[i].u );
        y = find( E[i].v );
        if (x == y)
            continue;
        set[x] = set[y];
        E[i].vis = true;
        sum++;
        ret += E[i].w;
    }    
    return ret;
}

struct point
{
    int x,y;
}P[MAXN];

int getdisSq(point a, point b)
{
    return (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y);
}

int main(void)
{
    int t;
    scanf("%d",&t);
    while (t--)
    {
        scanf("%d",&N);
        for(int i=1; i<=N; i++)
            scanf("%d%d",&P[i].x,&P[i].y);
        EN = 0;
        for(int i=1; i<N; i++)
        {
            for(int j=i+1; j<=N; j++)
            {
                int tmp = getdisSq(P[i],P[j]);
                if (100 <= tmp && tmp <= 1000000)
                    addedge(i,j,sqrt(1.0*tmp));
            }
        }
        double ans = kruskal();
        if (sum == N-1)
            printf("%.1lf\n",100*ans);
        else
            printf("oh!\n");
    }
    return 0;
}