Language: C++

#include <algorithm>
#include <atcoder/scc>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>
#define MOD 1000000007
#define MOD2 998244353
#define int long long
#define double long double
#define EPS 1e-9
//#define PI 3.14159265358979

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

using namespace std;

template < typename T >
ostream &operator<<(ostream &os, const vector< T > &A) {
	for (int i = 0; i < A.size(); i++)
		os << A[i] << " ";
	os << endl;
	return os;
}
template <>
ostream &operator<<(ostream &os, const vector< vector< int > > &A) {
	int N = A.size();
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < A[i].size(); j++)
			os << A[i][j] << " ";
		os << endl;
	}
	return os;
}
template < typename T, typename U >
ostream &operator<<(ostream &os, const pair< T, U > &p) {
	os << "(" << p.first << "," << p.second << ")";
	return os;
}

typedef pair< int, int > pii;
typedef long long ll;

struct edge {
	int from, to, d, c, i;
	edge(int _from = 0, int _to = 0, int _d = 0, int _c = 0) {
		from = _from;
		to = _to;
		d = _d;
		c = _c;
	}
	bool operator<(const edge &rhs) const {
		return (d == rhs.d) ? (c < rhs.c) : (d < rhs.d);
	}
};
struct aabb {
	int x1, y1, x2, y2;
	aabb(int x1, int y1, int x2, int y2) : x1(x1), y1(y1), x2(x2), y2(y2) {}
};

typedef vector< edge > edges;
typedef vector< edges > graph;
struct flow {
	int to, cap, rev, cost;
	flow(int to = 0, int cap = 0, int rev = 0, int cost = 0) : to(to), cap(cap), rev(rev), cost(cost) {}
};
typedef vector< vector< flow > > flows;

const int di[4] = {0, -1, 0, 1};
const int dj[4] = {-1, 0, 1, 0};
const int ci[5] = {0, 0, -1, 0, 1};
const int cj[5] = {0, -1, 0, 1, 0};
const ll LINF = LLONG_MAX / 2;
const int INF = INT_MAX / 2;
const double PI = acos(-1);

int pow2(int n) { return 1LL << n; }
template < typename T, typename U >
bool chmin(T &x, const U &y) {
	if (x > y) {
		x = y;
		return true;
	}
	return false;
}
template < typename T, typename U >
bool chmax(T &x, const U &y) {
	if (x < y) {
		x = y;
		return true;
	}
	return false;
}

template < typename A, size_t N, typename T >
void Fill(A (&array)[N], const T &val) {
	fill((T *)array, (T *)(array + N), val);
}
struct initializer {
	initializer() {
		cout << fixed << setprecision(20);
	}
};
initializer _____;

struct SCC {
	vector< vector< int > > G;

	vector< int > id;
	vector< vector< int > > G2;
	int s;
	int count2 = 0;
	void calc() {
		id.assign(G.size(), -1);
		vector< int > num(G.size(), -1);
		vector< int > low(G.size(), LINF);
		stack< int > st;
		int count = 0;
		count2 = 0;
		auto f = [&](auto &&f, int x) -> void {
			num[x] = low[x] = count++;
			st.push(x);
			for (auto j : G[x]) {
				if (num[j] == -1) {
					f(f, j);
					chmin(low[x], low[j]);
				} else {
					chmin(low[x], num[j]);
				}
			}
			if (low[x] == num[x]) {
				while (1) {
					int y = st.top();
					st.pop();
					num[y] = LINF;
					id[y] = count2;
					if (x == y)
						break;
				}
				count2++;
			}
		};
		rep(i, G.size()) if (num[i] == -1) f(f, i);
		rep(i, G.size()) id[i] = count2 - 1 - id[i];
	}
	void topologicalSort() {
		calc();
		G2.resize(count2);
		rep(i, G.size()) {
			rep(j, G[i].size()) {
				int x = i, y = G[i][j];
				if (id[x] != id[y]) {
					G2[id[x]].push_back(id[y]);
				}
			}
		}
	}
	SCC(const vector< vector< int > > &_G) {
		G.resize(_G.size());
		rep(i, _G.size()) {
			rep(j, _G[i].size()) {
				G[i].push_back(_G[i][j]);
			}
		}
	}
	SCC(int N) {
		G.resize(N);
	}
};

int N, M, K, T, Q, H, W;
signed main() {
	cin >> N >> M;
	SCC sc(N);
	atcoder::scc_graph asc(N);
	rep(i, M) {
		int a, b;
		cin >> a >> b;
		sc.G[a].push_back(b);
		asc.add_edge(a, b);
	}
	sc.topologicalSort();
	vector< vector< int > > &G2 = sc.G2;
	//cerr << G2;
	//cerr << sc.id;
	//cerr << asc.scc();

	vector< vector< int > > ans(sc.count2);
	rep(i, N) {
		ans[sc.id[i]].push_back(i);
	}
	cout << ans.size() << endl;
	rep(i, ans.size()) {
		cout << ans[i].size() << " ";
		rep(j, ans[i].size()) {
			cout << ans[i][j] << " ";
		}
		cout << endl;
	}
	return 0;
}

Compiler output:
a.cc:2:10: fatal error: atcoder/scc: No such file or directory
    2 | #include <atcoder/scc>
      |          ^~~~~~~~~~~~~
compilation terminated.