tarjan1

#include<iostream>
#include<cstring>
using namespace std;
struct node
{
    int v;
    int next;
}edge[1010];
int dfn[1010],low[1010],heads[1010];
int cnt,visit[1010],stack[1010],tot;
int idx,ans;
void add(int x,int y)
{
    edge[++cnt].next=heads[x];
    edge[cnt].v=y;
    heads[x]=cnt;
    return;
}
void tarjan(int x)
{
    dfn[x]=low[x]=++tot;
    stack[++idx]=x;
    visit[x]=1;
    for(int i=heads[x];i!=-1;i=edge[i].next)
    {
        if(dfn[edge[i].v]==0)
        {
            tarjan(edge[i].v);
            low[x]=min(low[x],low[edge[i].v]);
        }
        else if(visit[edge[i].v])
        {
            low[x]=min(low[x],dfn[edge[i].v]);
        }
    }
    if(low[x]==dfn[x])
    {
        do
        {
            cout<<stack[idx];
            visit[stack[idx]]=0;
            idx--;
        }while(x!=stack[idx+1]);
        cout<<endl;
    }
    return;
}
int main()
{
    memset(heads,-1,sizeof(heads));
    int n,m;
    cin>>n>>m;
    int x,y;
    for(int i=1;i<=m;i++)
    {
        cin>>x>>y;
        add(x,y);
    }
    for(int i=1;i<=n;i++)
    {
        if(dfn[i]==0)
        {
            tarjan(i);
        }
    }
    return 0;
}