#line 1 "test/yj_scc.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/scc"
#include <cstdio>
#include <algorithm>
#include <vector>
#line 1 "Graph/adjacency_list.cpp"
/**
* @brief 重みつきグラフの隣接リスト
* @author えびちゃん
*/
#include <cstddef>
#line 11 "Graph/adjacency_list.cpp"
#include <type_traits>
#line 13 "Graph/adjacency_list.cpp"
template <typename WeightType>
class weighted_edge {
public:
using size_type = size_t;
using weight_type = WeightType;
protected:
size_type M_src, M_dst;
weight_type M_weight;
public:
weighted_edge() = default;
weighted_edge(weighted_edge const&) = default;
weighted_edge(weighted_edge&&) = default;
weighted_edge(size_type s, size_type d, weight_type w):
M_src(s), M_dst(d), M_weight(w)
{}
weighted_edge& operator =(weighted_edge const&) = default;
weighted_edge& operator =(weighted_edge&&) = default;
bool operator <(weighted_edge const& other) const {
if (M_weight < other.M_weight) return true;
if (other.M_weight < M_weight) return false;
if (M_src != other.M_src) return M_src < other.M_src;
return M_dst < other.M_dst;
}
size_type source() const { return M_src; }
size_type target() const { return M_dst; }
weight_type weight() const { return M_weight; }
};
struct directed_tag {};
struct undirected_tag {};
template <typename Edge, typename Directedness>
class adjacency_list {
public:
using size_type = size_t;
using edge_type = Edge;
using weight_type = typename Edge::weight_type;
private:
std::vector<std::vector<edge_type>> M_g;
public:
adjacency_list() = default;
adjacency_list(adjacency_list const&) = default;
adjacency_list(adjacency_list&&) = default;
explicit adjacency_list(size_type n): M_g(n) {}
template <typename... Args>
void emplace(size_type src, size_type dst, Args... args) {
M_g[src].emplace_back(src, dst, args...);
if (std::is_same<Directedness, undirected_tag>::value)
M_g[dst].emplace_back(dst, src, args...);
}
void sort_by_index() {
auto cmp = [](auto const& e1, auto const& e2) {
return e1.target() < e2.target();
};
for (auto v: M_g) std::sort(v.begin(), v.end(), cmp);
}
size_type size() const { return M_g.size(); }
auto const& operator [](size_type i) const { return M_g[i]; }
};
#line 1 "Graph/scc.cpp"
/**
* @brief 強連結成分分解
* @author えびちゃん
*/
#line 11 "Graph/scc.cpp"
#line 1 "utility/make/fix_point.cpp"
/**
* @brief ラムダ式の再帰
* @author えびちゃん
*/
#ifndef H_make_fix_point
#define H_make_fix_point
#include <utility>
template <typename Fn>
class fix_point: Fn {
public:
explicit constexpr fix_point(Fn&& f) noexcept: Fn(std::forward<Fn>(f)) {}
template <typename... Args>
constexpr decltype(auto) operator ()(Args&&... args) const {
return Fn::operator ()(*this, std::forward<Args>(args)...);
}
};
template <typename Fn>
static inline constexpr decltype(auto) make_fix_point(Fn&& f) noexcept {
return fix_point<Fn>{std::forward<Fn>(f)};
}
#endif /* !defined(H_make_fix_point) */
#line 14 "Graph/scc.cpp"
template <typename AdjacencyList>
auto strongly_connected_components(AdjacencyList const& g) {
size_t n = g.size();
adjacency_list<weighted_edge<bool>, directed_tag> h(n);
for (size_t v = 0; v < n; ++v)
for (auto const& e: g[v]) h.emplace(e.target(), e.source(), 1);
std::vector<bool> used(n);
std::vector<size_t> vs;
auto dfs = make_fix_point([&](auto f, size_t v) -> void {
used[v] = true;
for (auto const& e: g[v])
if (!used[e.target()]) f(e.target());
vs.push_back(v);
});
for (size_t v = 0; v < n; ++v)
if (!used[v]) dfs(v);
used.assign(n, false);
std::vector<size_t> cmp(n);
size_t num = 0;
auto rdfs = make_fix_point([&](auto f, size_t v) -> void {
used[v] = true;
cmp[v] = num;
for (auto const& e: h[v])
if (!used[e.target()]) f(e.target());
});
for (size_t v = vs.size(); v--;)
if (!used[vs[v]])
rdfs(vs[v]), ++num;
return cmp;
}
#line 9 "test/yj_scc.test.cpp"
int main() {
size_t n, m;
scanf("%zu %zu", &n, &m);
adjacency_list<weighted_edge<int>, directed_tag> g(n);
for (size_t i = 0; i < m; ++i) {
size_t u, v;
scanf("%zu %zu", &u, &v);
g.emplace(u, v, 1);
}
auto scc = strongly_connected_components(g);
size_t k = *std::max_element(scc.begin(), scc.end()) + 1;
std::vector<std::vector<size_t>> ts(k);
for (size_t i = 0; i < n; ++i)
ts[scc[i]].push_back(i);
printf("%zu\n", k);
for (size_t i = 0; i < k; ++i) {
printf("%zu", ts[i].size());
for (auto v: ts[i]) printf(" %zu", v);
puts("");
}
}
test/yj_scc.test.cpp