test/graph/scc_graph.test.cpp

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Last update: 2025-03-18 03:40:16+09:00
Problem: https://judge.yosupo.jp/problem/scc

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Code

#define PROBLEM "https://judge.yosupo.jp/problem/scc"

#include "../../graph/scc_graph.hpp"


#include <iostream>


int main() {
    int n, m;
    std::cin >> n >> m;
    ebi::scc_graph g(n);
    for (int i = 0; i < m; ++i) {
        int a, b;
        std::cin >> a >> b;
        g.add_edge(a, b);
    }
    auto scc = g.scc();
    int sz = scc.size();
    std::cout << sz << '\n';
    for (int i = 0; i < sz; ++i) {
        std::cout << scc[i].size();
        for (auto v : scc[i]) {
            std::cout << " " << v;
        }
        std::cout << '\n';
    }
}

#line 1 "test/graph/scc_graph.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/scc"

#line 2 "graph/scc_graph.hpp"

#include <algorithm>

#include <vector>


#line 2 "data_structure/simple_csr.hpp"

#include <ranges>
#include <utility>
#line 6 "data_structure/simple_csr.hpp"

namespace ebi {

template <class E> struct simple_csr {
    simple_csr() = default;

    simple_csr(int n, const std::vector<std::pair<int, E>>& elements)
        : start(n + 1, 0), elist(elements.size()) {
        for (auto e : elements) {
            start[e.first + 1]++;
        }
        for (auto i : std::views::iota(0, n)) {
            start[i + 1] += start[i];
        }
        auto counter = start;
        for (auto [i, e] : elements) {
            elist[counter[i]++] = e;
        }
    }

    simple_csr(const std::vector<std::vector<E>>& es)
        : start(es.size() + 1, 0) {
        int n = es.size();
        for (auto i : std::views::iota(0, n)) {
            start[i + 1] = (int)es[i].size() + start[i];
        }
        elist.resize(start.back());
        for (auto i : std::views::iota(0, n)) {
            std::copy(es[i].begin(), es[i].end(), elist.begin() + start[i]);
        }
    }

    int size() const {
        return (int)start.size() - 1;
    }

    const auto operator[](int i) const {
        return std::ranges::subrange(elist.begin() + start[i],
                                     elist.begin() + start[i + 1]);
    }
    auto operator[](int i) {
        return std::ranges::subrange(elist.begin() + start[i],
                                     elist.begin() + start[i + 1]);
    }

    const auto operator()(int i, int l, int r) const {
        return std::ranges::subrange(elist.begin() + start[i] + l,
                                     elist.begin() + start[i + 1] + r);
    }
    auto operator()(int i, int l, int r) {
        return std::ranges::subrange(elist.begin() + start[i] + l,
                                     elist.begin() + start[i + 1] + r);
    }

  private:
    std::vector<int> start;
    std::vector<E> elist;
};

}  // namespace ebi
#line 2 "graph/base.hpp"

#include <cassert>
#include <iostream>
#line 7 "graph/base.hpp"

#line 9 "graph/base.hpp"

namespace ebi {

template <class T> struct Edge {
    int from, to;
    T cost;
    int id;
};

template <class E> struct Graph {
    using cost_type = E;
    using edge_type = Edge<cost_type>;

    Graph(int n_) : n(n_) {}

    Graph() = default;

    void add_edge(int u, int v, cost_type c) {
        assert(!prepared && u < n && v < n);
        buff.emplace_back(u, edge_type{u, v, c, m});
        edges.emplace_back(edge_type{u, v, c, m++});
    }

    void add_undirected_edge(int u, int v, cost_type c) {
        assert(!prepared && u < n && v < n);
        buff.emplace_back(u, edge_type{u, v, c, m});
        buff.emplace_back(v, edge_type{v, u, c, m});
        edges.emplace_back(edge_type{u, v, c, m});
        m++;
    }

    void read_tree(int offset = 1, bool is_weighted = false) {
        read_graph(n - 1, offset, false, is_weighted);
    }

    void read_parents(int offset = 1) {
        for (auto i : std::views::iota(1, n)) {
            int p;
            std::cin >> p;
            p -= offset;
            add_undirected_edge(p, i, 1);
        }
        build();
    }

    void read_graph(int e, int offset = 1, bool is_directed = false,
                    bool is_weighted = false) {
        for (int i = 0; i < e; i++) {
            int u, v;
            std::cin >> u >> v;
            u -= offset;
            v -= offset;
            if (is_weighted) {
                cost_type c;
                std::cin >> c;
                if (is_directed) {
                    add_edge(u, v, c);
                } else {
                    add_undirected_edge(u, v, c);
                }
            } else {
                if (is_directed) {
                    add_edge(u, v, 1);
                } else {
                    add_undirected_edge(u, v, 1);
                }
            }
        }
        build();
    }

    void build() {
        assert(!prepared);
        csr = simple_csr<edge_type>(n, buff);
        buff.clear();
        prepared = true;
    }

    int size() const {
        return n;
    }

    int node_number() const {
        return n;
    }

    int edge_number() const {
        return m;
    }

    edge_type get_edge(int i) const {
        assert(prepared);
        return edges[i];
    }

    std::vector<edge_type> get_edges() const {
        assert(prepared);
        return edges;
    }

    const auto operator[](int i) const {
        assert(prepared);
        return csr[i];
    }
    auto operator[](int i) {
        assert(prepared);
        return csr[i];
    }

  private:
    int n, m = 0;

    std::vector<std::pair<int, edge_type>> buff;

    std::vector<edge_type> edges;
    simple_csr<edge_type> csr;
    bool prepared = false;
};

}  // namespace ebi
#line 8 "graph/scc_graph.hpp"

namespace ebi {

struct scc_graph {
  private:
    std::vector<std::pair<int, int>> edges, redges;
    simple_csr<int> g, rg;
    int n, k;

    std::vector<int> vs, cmp;
    std::vector<bool> seen;

    void dfs(int v) {
        seen[v] = true;
        for (auto &nv : g[v]) {
            if (!seen[nv]) dfs(nv);
        }
        vs.emplace_back(v);
    }

    void rdfs(int v) {
        cmp[v] = k;
        for (auto nv : rg[v]) {
            if (cmp[nv] < 0) {
                rdfs(nv);
            }
        }
    }

  public:
    scc_graph(int n_) : n(n_) {}

    void add_edge(int from, int to) {
        edges.emplace_back(from, to);
        redges.emplace_back(to, from);
    }

    std::vector<std::vector<int>> scc() {
        g = simple_csr<int>(n, edges);
        rg = simple_csr<int>(n, redges);
        edges.clear();
        redges.clear();
        seen.assign(n, false);
        for (int i = 0; i < n; i++) {
            if (!seen[i]) {
                dfs(i);
            }
        }
        std::reverse(vs.begin(), vs.end());
        cmp.assign(n, -1);
        k = 0;
        for (auto &v : vs) {
            if (cmp[v] < 0) {
                rdfs(v);
                k++;
            }
        }
        std::vector<std::vector<int>> res(k);
        for (int i = 0; i < n; i++) {
            res[cmp[i]].emplace_back(i);
        }
        return res;
    }

    std::vector<int> scc_id() {
        return cmp;
    }

    bool same(int u, int v) {
        return cmp[u] == cmp[v];
    }

    Graph<int> create_graph() {
        std::vector<std::pair<int, int>> es;
        for (int i = 0; i < n; i++) {
            int v = cmp[i];
            for (auto to : g[i]) {
                int nv = cmp[to];
                if (v == nv) continue;
                es.emplace_back(v, nv);
            }
        }
        std::sort(es.begin(), es.end());
        es.erase(std::unique(es.begin(), es.end()), es.end());
        Graph<int> t(k);
        for (auto [v, nv] : es) {
            t.add_edge(v, nv, 1);
        }
        t.build();
        return t;
    }
};

}  // namespace ebi
#line 4 "test/graph/scc_graph.test.cpp"

#line 6 "test/graph/scc_graph.test.cpp"

int main() {
    int n, m;
    std::cin >> n >> m;
    ebi::scc_graph g(n);
    for (int i = 0; i < m; ++i) {
        int a, b;
        std::cin >> a >> b;
        g.add_edge(a, b);
    }
    auto scc = g.scc();
    int sz = scc.size();
    std::cout << sz << '\n';
    for (int i = 0; i < sz; ++i) {
        std::cout << scc[i].size();
        for (auto v : scc[i]) {
            std::cout << " " << v;
        }
        std::cout << '\n';
    }
}