Language: C++

#include <bits/stdc++.h>
#define FASTIO
using namespace std;

using ll = long long;
using Vi = std::vector<int>;
using Vl = std::vector<ll>;
using Pii = std::pair<int, int>;
using Pll = std::pair<ll, ll>;

constexpr int I_INF = std::numeric_limits<int>::max();
constexpr ll L_INF = std::numeric_limits<ll>::max();

template <typename T1, typename T2>
inline bool chmin(T1& a, const T2& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T1, typename T2>
inline bool chmax(T1& a, const T2& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

class Prints {
private:
    class __Prints {
    public:
        __Prints(const char* sep, const char* term) : sep(sep), term(term) {}
        template <class... Args>
        void operator()(const Args&... args) const { print(args...); }
        template <typename T>
        void pvec(const T& vec, size_t sz) const {
            for (size_t i = 0; i < sz; i++)
                std::cout << vec[i] << (i == sz - 1 ? term : sep);
        }
        template <typename T>
        void pmat(const T& mat, size_t h, size_t w) {
            for (size_t i = 0; i < h; i++)
                for (size_t j = 0; j < w; j++)
                    std::cout << mat[i][j] << (j == w - 1 ? term : sep);
        }

    private:
        const char *sep, *term;
        void print() const { std::cout << term; }
        void print_rest() const { std::cout << term; }
        template <class T, class... Tail>
        void print(const T& head, const Tail&... tail) const { std::cout << head, print_rest(tail...); }
        template <class T, class... Tail>
        void print_rest(const T& head, const Tail&... tail) const { std::cout << sep << head, print_rest(tail...); }
    };

public:
    Prints() {}
    __Prints operator()(const char* sep = " ", const char* term = "\n") const { return __Prints(sep, term); }
};

Prints prints;

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

using Graph = std::vector<std::vector<int>>;

int scc(std::vector<int>& res, const Graph& g) {
    const int sz = static_cast<int>(g.size());
    Graph rg(sz);
    for (int i = 0; i < sz; i++) {
        for (const auto& v : g[i]) {
            rg[v].emplace_back(i);
        }
    }
    std::vector<int> vs;
    bool used[sz] = {};
    auto dfs1 = [&](auto&& self, int idx) -> void {
        used[idx] = true;
        for (const auto& v : g[idx]) {
            if (!used[v]) self(self, v);
        }
        vs.emplace_back(idx);
    };
    auto dfs2 = [&](auto&& self, int idx, int k) -> void {
        used[idx] = true;
        res[idx] = k;
        for (const auto& v : rg[idx]) {
            if (!used[v]) self(self, v, k);
        }
    };
    res.resize(sz);
    for (int i = 0; i < sz; i++) {
        if (!used[i]) dfs1(dfs1, i);
    }
    memset(used, 0, sizeof(used));
    int ord = 0;
    for (int i = sz - 1; i >= 0; i--) {
        if (!used[vs[i]]) dfs2(dfs2, vs[i], ord++);
    }
    return ord;
}

void solve() {
    int N, M;
    cin >> N >> M;
    Graph g(N);
    for (ll i = 0; i < M; i++) {
        int a, b;
        cin >> a >> b;
        g[a].emplace_back(b);
    }

    Vi res;
    int scn = scc(res, g);

    vector<Vi> ans(scn);
    for (ll i = 0; i < N; i++) {
        ans[res[i]].emplace_back(i);
    }

    prints()(scn);
    for (ll i = 0; i < scn; i++) {
        prints("", " ")(ans[i].size());
        prints().pvec(ans[i], ans[i].size());
    }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

int main() {
#ifdef FASTIO
    std::cin.tie(nullptr), std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);
#endif
#ifdef FILEINPUT
    std::ifstream ifs("./in_out/input.txt");
    std::cin.rdbuf(ifs.rdbuf());
#endif
#ifdef FILEOUTPUT
    std::ofstream ofs("./in_out/output.txt");
    std::cout.rdbuf(ofs.rdbuf());
#endif
    std::cout << std::setprecision(18) << std::fixed;
    solve();
    std::cout << std::flush;
    return 0;
}

Compiler output:
a.cc: In function 'int scc(std::vector<int>&, const Graph&)':
a.cc:81:17: error: use of deleted function 'scc(std::vector<int>&, const Graph&)::<lambda(auto:28&&, int)>::~<lambda>()'
   81 |     auto dfs1 = [&](auto&& self, int idx) -> void {
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   82 |         used[idx] = true;
      |         ~~~~~~~~~~~~~~~~~
   83 |         for (const auto& v : g[idx]) {
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   84 |             if (!used[v]) self(self, v);
      |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   85 |         }
      |         ~        
   86 |         vs.emplace_back(idx);
      |         ~~~~~~~~~~~~~~~~~~~~~
   87 |     };
      |     ~            
a.cc:81:19: note: 'scc(std::vector<int>&, const Graph&)::<lambda(auto:28&&, int)>::~<lambda>()' is implicitly deleted because the default definition would be ill-formed:
   81 |     auto dfs1 = [&](auto&& self, int idx) -> void {
      |                   ^
a.cc:88:17: error: use of deleted function 'scc(std::vector<int>&, const Graph&)::<lambda(auto:29&&, int, int)>::~<lambda>()'
   88 |     auto dfs2 = [&](auto&& self, int idx, int k) -> void {
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   89 |         used[idx] = true;
      |         ~~~~~~~~~~~~~~~~~
   90 |         res[idx] = k;
      |         ~~~~~~~~~~~~~
   91 |         for (const auto& v : rg[idx]) {
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   92 |             if (!used[v]) self(self, v, k);
      |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   93 |         }
      |         ~        
   94 |     };
      |     ~            
a.cc:88:19: note: 'scc(std::vector<int>&, const Graph&)::<lambda(auto:29&&, int, int)>::~<lambda>()' is implicitly deleted because the default definition would be ill-formed:
   88 |     auto dfs2 = [&](auto&& self, int idx, int k) -> void {
      |                   ^