RE求条必关

#include<bits/stdc++.h>
using namespace std;
const int N=1e4+10,M=1e5+10;
int n,m,h[N],e[N],ne[M],id;
int dfn[N],low[N],idx=0,ins[N],scc[N],ans[N][N],siz[N],cnt,f[N];
stack<int>st;
void add(int a,int b){
	id++;
	e[id]=b;
	ne[id]=h[a];
	h[a]=id;
}
//入x的时候,盖戳,入栈
//枚举x的相邻点y 
//1.未访问(树枝边)(1)深搜y(2)更新low[x] 
//2.已访问在栈中(返祖边)(1)更新low[x] 
//3.已访问不在栈中(横叉边)
//离开x的时候,出栈,更新scc
//处理非连通图 
void tarjan(int u){
	dfn[u]=++idx;
	low[u]=idx;
	ins[u]=true;
	st.push(u);
	for(int i=h[u];i;i=ne[i]){
		int v=e[i];
		if(!dfn[v]){
			tarjan(v);
			low[u]=min(low[u],low[v]); 
		}
		else if(ins[v])low[u]=min(low[u],dfn[v]);
	}
	if(dfn[u]==low[u]){
		++cnt;
		while(1){
			int v=st.top();
			st.pop();
			ins[v]=false;
			scc[v]=cnt;
			ans[cnt][++siz[cnt]]=v;
			if(v==u)break;
		}
	}
}
int main(){
	cin>>n>>m;
	memset(h,0,sizeof(h));
	for(int i=1;i<=m;i++){
		int a,b;
		cin>>a>>b;
		add(a,b);
	} 
	for(int i=1;i<=n;i++){
		if(!dfn[i]){
			tarjan(i);
		}
	}
	cout<<cnt<<endl;
	for(int i=1;i<=cnt;i++){
		sort(ans[i]+1,ans[i]+siz[i]+1);
	}
	for(int i=1;i<=n;i++){
		if(f[i])continue;
		for(int j=1;j<=siz[scc[i]];j++){
			f[ans[scc[i]][j]]=1;
			cout<<ans[scc[i]][j]<<" ";
		}
		cout<<endl; 
	}
	return 0;
}