#include <bits/stdc++.h>
#define maxn 1010
using namespace std;
const double eps = 1e-6;
struct edge{
	int to,next;
	double dis;
}e[maxn];
struct edge1{
	int u,v;
	double w;
}e1[maxn];
struct node{
	int x,y;
}pos[maxn];
int n,m,head[maxn],cnt,a,b,f[maxn];
inline int read(){
	int x = 0,f = 1;
	char ch = getchar();
	while(!isdigit(ch)){if(ch == '-') f = -1;ch = getchar();}
	while(isdigit(ch)){x = x * 10 + ch - '0';ch = getchar();}
	return f * x;
}
/*inline void add_edge(int u,int v,double d){
	e[++cnt].to = v;
	e[cnt].dis = d;
	e[cnt].next = head[u];
	head[u] = cnt;
}*/
inline double getDis(int p,int q){
	int tx = abs(pos[p].x - pos[q].x);
	int ty = abs(pos[p].y - pos[q].y);
	double ans = sqrt(tx * tx + ty * ty);
	return ans;
}
inline int find(int x){
	if(f[x] != x)
		f[x] = find(f[x]);
	return f[x];
}
inline bool cmp(edge1 p,edge1 q){
	return p.w - q.w < eps;
}
int main(){
	n = read(),m = read();
	for(int i = 1;i <= n;i++){
		f[i] = i;
	}
	for(int i = 1;i <= n;i++){
		a = read(),b = read();
		pos[i].x = a;
		pos[i].y = b;
	}
	for(int i = 1;i <= m;i++){
		a = read(),b = read();
		int fa = find(a);
		int fb = find(b);
		if(fa != fb)
			f[fb] = f[fa];
	}
	int c = 0,ti,tj;
	for(int i = 1;i <= n;i++)
		for(int j = i + 1;j <= n;j++){
			ti = find(i),tj = find(j);
			if(ti != tj && i != j){
				e1[++cnt].u = i;
				e1[cnt].v = j;
				e1[cnt].w = getDis(i,j);
				// add_edge(i,j,getDis(i,j));
			}
		}
	sort(e1 + 1,e1 + 1 + cnt,cmp);
	double sum = 0.00;
	for(int i = 1;i <= cnt;i++){
		ti = find(e1[i].u);
		tj = find(e1[i].v);
		if(ti != tj){
			f[tj] = f[ti];
			sum += e1[i].w;
			c++;
		}
		if(c == n - m - 1){
			break;
		}
	}
	printf("%.2f",sum);
	return 0;
}

如果把getDis函数中abs去掉就WA了

但是有3个点AC了

请dalao指教