0分求调

#include<bits/stdc++.h>
using namespace std;
const int MAXN=2e6+10;
int num,ans;
int n,m;
struct linkstar{
    int from,to,w,next;
}edge[2*MAXN];
int head[MAXN],dfn[MAXN],low[MAXN],vis[MAXN];
vector<int> dcc[MAXN];
bool bridge[2*MAXN];
int escnt,tim,root;
vector<int> vec;
void add(int u,int v)
{
    edge[++escnt].from=u;
    edge[escnt].to=v;
    edge[escnt].next=head[u];
    head[u]=escnt;
}
void tarjan(int u,int fa)
{
    dfn[u]=low[u]=++tim;
    for (int i=head[u];i!=-1;i=edge[i].next){
        int v=edge[i].to;
        if(dfn[v]==0){
            tarjan(v,i);
            low[u]=min(low[u],low[v]);
            if(low[v]>dfn[u]) bridge[i]=bridge[i^1]=1; 
        }
        else if(i!=(fa^1)){
            low[u]=min(low[u],dfn[v]);
        }
    }
}
void dfs(int u)
{
    vis[u]=num;
    if(u) dcc[num].push_back(u);
    for (int i=head[u];i!=-1;i=edge[i].next){
        int v=edge[i].to;
        if(bridge[i]) continue;
        if(!vis[v]) dfs(v);
    }
}
int main()
{
    memset(head,-1,sizeof(head));
    cin>>n>>m;
    int x,y;
    for (int i=1;i<=m;i++){
        cin>>x>>y;
        if(x==y) continue;
        add(x,y);
        add(y,x);
    }
    for (int i=1;i<=n;i++){
        if(!dfn[i]) tarjan(i,0);
    }
    for (int i=1;i<=n;i++){
        if(!vis[i]){
            num++;
            dfs(i);
        }
    }
    cout<<num<<endl;
    for (int i=1;i<=num;i++){
        cout<<dcc[i].size()<<" ";
        for (int j:dcc[i]) cout<<j<<" ";
        cout<<endl;
    }
    return 0;
}