WA0pts求调

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

const int N = 1e4+5,M = 1e5+5;

struct node
{
    int u,v;
}p[M<<1];

int head[N],k,n,m,dfn[N],low[N],t,st[N],top,num,col[N];
bool vis[N],vis2[N];
vector<int> ans[N];

void add(int x,int y)
{
    p[++k].u = head[x];
    p[k].v = y;
    head[x] = k;
}

void dfs(int son)
{
    t++;
    dfn[son] = low[son] = t;
    vis[son] = 1;
    st[++top] = son;
    for(int i=head[son];i;i=p[i].u)
    {
        int to = p[i].v;
        if(!dfn[to])
        {
            dfs(to);
            low[son] = min(low[son],low[to]);
        }
        else if(vis[to]) low[son] = min(low[son],low[to]);
    }
    if(dfn[son]==low[son])
    {
        num++;
        ans[num].push_back(son);
        while(st[top]!=son)
        {
            col[st[top]] = num;
            vis[st[top]] = 0;
            ans[num].push_back(st[top]);
            top--;
        }
        top--;
        vis[son] = 0;
        col[son] = num;
    }
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin >> n >> m;
    for(int i=1,x,y;i<=m;i++)
    {
        if(x==y) continue;
        cin >> x >> y;
        add(x,y);
    }
    for(int i=1;i<=n;i++)
        if(!dfn[i]) dfs(i);
    cout << num << endl;
    for(int i=1;i<=num;i++) sort(ans[i].begin(),ans[i].end());
    for(int i=1;i<=n;i++)
    {
        if(vis2[col[i]]) continue;
        vis2[col[i]] = 1;
        for(int j=0;j<ans[col[i]].size();j++) cout << ans[col[i]][j] << ' ';
        cout << endl;
    }
    return 0;
}