@[Rhss](/user/684890)
```cpp
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<queue>
#include<vector>
using namespace std;
int n,m,c[10010],ans = 0;
vector<int> adj[10010];
bool bfs()
{
memset(c,0,sizeof(c));
for (int u = 1;u <= n;u++)
if (c[u] == 0)
{
int cnt1 = 1,cnt2 = 0;
c[u] = 1;
queue<int> q;
q.push(u);
while(!q.empty())
{
int v = q.front();
q.pop();
for (int w:adj[v])
{
if (c[w] == 0)
{
c[w] = -c[v];
q.push(w);
if (c[w] == 1) cnt1++;
else cnt2++;
}
else if (c[w] == c[v])
return false;
}
}
ans += min(cnt1,cnt2);
}
return true;
}
int main()
{
scanf("%d%d",&n,&m);
for (int i = 1;i <= m;i++)
{
int x,y;
scanf("%d%d",&x,&y);
adj[x].push_back(y);
adj[y].push_back(x);
}
if (!bfs()) printf("Impossible\n");
else printf("%d\n",ans);
return 0;
}
```
by codejiahui @ 2023-05-10 13:27:18
@[Rhss](/user/684890) 不能用最小点覆盖来做，最小点覆盖中的点之间可能会有边
by shysacscsc @ 2024-01-31 23:12:38