更正代码后是60分了，t++只取决于边不为0的时候
```cpp
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
const int N = 1e6;
int n,m;
int ans = 0;
struct edge{
vector<int> v;
int point;
};
edge a[N];
int f[N];
void init(){
for(int i = 1;i<=n;++i) f[i] = i;
}
int findfather(int x){
if(x==f[x]) return x;
return f[x] = findfather(f[x]);
}
void merge(int a,int b){
int fa = findfather(a);
int fb = findfather(b);
if(fa!=fb){
f[fa] = fb;
}
}
bool cmp(edge a,edge b){
return a.v.size()>b.v.size();
}
int main(){
cin>>n>>m;
init();
for(int i = 1;i<=m;++i){
int x,y;
cin>>x>>y;
a[x].point = x;
a[x].v.push_back(y);
a[y].point = y;
a[y].v.push_back(x);
}
sort(a+1,a+n+1,cmp);
int t = 0;
for(int i = 1;i<=n;++i){
if(findfather(a[i].point) == a[i].point){
for(int j = 0;j<a[i].v.size();++j){
merge(a[i].v[j],a[i].point);
}
ans+=a[i].v.size();
//单个点完全独立，那么就不需要放出河蟹
if(a[i].v.size()!=0) t++;
}
}
if(ans<m) cout<<"Impossible";
else cout<<t;
return 0;
}
```
by Rhss @ 2022-10-25 15:26:13