模板題，沒啥好說的。。

最小樹形圖的解法見：http://www.cnblogs.com/vongang/archive/2012/07/18/2596851.html

CODE：

#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define MAX 50010
#define INF (min_dis[0])
using namespace std;

struct Point{
	int x,y;
}point[MAX];

int points,edges;
int head[MAX],total;
int next[MAX],aim[MAX],from[MAX];
double length[MAX];

double min_dis[MAX];
int father[MAX];

int vis[MAX],num[MAX],cnt;

inline void Initialize();
inline void Add(int x,int y,double len);
inline double Calc(Point a,Point b);
double DirectedMST(int root);

int main()
{
	while(scanf("%d%d",&points,&edges) != EOF) {
		Initialize();
		for(int i = 1;i <= points; ++i)
			scanf("%d%d",&point[i].x,&point[i].y);
		for(int x,y,i = 1;i <= edges; ++i) {
			scanf("%d%d",&x,&y);
			if(x != y)	Add(x,y,Calc(point[x],point[y]));
		}
		double ans = DirectedMST(1);
		if(ans == -1)	puts("poor snoopy");
		else	printf("%.2lf\n",ans);
	}
	return 0;
}

inline void Initialize()
{
	total = 0;
	memset(head,0,sizeof(head));
}

inline void Add(int x,int y,double len)
{
	next[++total] = head[x];
	aim[total] = y;
	length[total] = len;
	from[total] = x;
	head[x] = total;
}

inline double Calc(Point a,Point b)
{
	return sqrt((double)(a.x - b.x) * (a.x - b.x) + 
				(double)(a.y - b.y) * (a.y - b.y));
}

double DirectedMST(int root)
{
	double re = 0;
	while(1) {
		memset(min_dis,0x43,sizeof(min_dis));
		for(int i = 1;i <= total; ++i) {
			if(length[i] < min_dis[aim[i]] && from[i] != aim[i]) {
				min_dis[aim[i]] = length[i];
				father[aim[i]] = from[i];
			}
		}
		for(int i = 1;i <= points; ++i)
			if(i != root && min_dis[i] == INF)
				return -1;

		memset(vis,0,sizeof(vis));
		memset(num,0,sizeof(num));
		min_dis[root] = 0;
		cnt = 0;
		for(int i = 1;i <= points; ++i) {
			re += min_dis[i];
			int now = i;
			while(vis[now] != i && !num[now] && now != root) {
				vis[now] = i;
				now = father[now];
			}
			if(now != root && !num[now]) {
				++cnt;
				for(int j = father[now];j != now;j = father[j])
					num[j] = cnt;
				num[now] = cnt;
			}
		}
		if(!cnt)	break;
		for(int i = 1;i <= points; ++i)
			if(!num[i])	num[i] = ++cnt;
		for(int i = 1;i <= edges; ++i) {
			if(num[from[i]] != num[aim[i]] && num[aim[i]] <= cnt)
				length[i] -= min_dis[aim[i]];
			from[i] = num[from[i]];
			aim[i] = num[aim[i]];
		}
		points = cnt;
		root = num[root]; 
	}
	return re;
}