cycle_detection.cpp

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define PI acos(-1)
#define pb push_back
#define int long long int
#define pi pair<int, int>
#define pii pair<int, pi>
#define fir first
#define sec second
#define MAXN 205
#define MAXP 100001
#define mod 1000000007

int n, m, idx;
vector<int> cycles[MAXN];
vector<int> adj[MAXN];
int color[MAXN];
int parent[MAXN];
int ans[MAXN];

void dfs(int u, int p)
{
  if (color[u] == 2)
    return;
  if (color[u] == 1)
  {
    idx++;
    int curr = p;
    ans[curr] = idx;
    cycles[idx].pb(curr);
    while (curr != u)
    {
      curr = parent[curr];
      cycles[idx].pb(curr);
      ans[curr] = idx;
    }
    return;
  }
  parent[u] = p;
  color[u] = 1;
  for (auto const &v : adj[u])
    if (v != parent[u])
      dfs(v, u);
  color[u] = 2;
}
signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> m;
  for (int i = 0; i < m; i++)
  {
    int a, b;
    cin >> a >> b;
    a--, b--;
    adj[a].pb(b);
    adj[b].pb(a);
  }
  for (int i = 0; i < n; i++)
    if (!color[i])
      dfs(i, -1);
  cout << idx << endl;
  for (int i = 1; i <= idx; i++)
  {
    cout << cycles[i].size() << endl;
    for (auto const &j : cycles[i])
      cout << j + 1 << " ";
    cout << endl;
  }
  return 0;
}