verify/lc_graph/lc_scc.test.cpp

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Last update: 2024-01-25 10:46:02+09:00
Problem: https://judge.yosupo.jp/problem/scc

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Code

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

#include <bits/stdc++.h>

#include "graph/graph_template.hpp"
#include "graph/read_graph.hpp"
#include "graph/strongly_connected_component.hpp"

int main() {
    int N, M;
    std::cin >> N >> M;
    auto G = read_graph<int>(N, M, false, true, 0);
    auto scc = strongly_connected_component(G);
    std::cout << scc.size() << '\n';
    for (auto& vec : scc) {
        std::cout << vec.size();
        for (auto& vi : vec) std::cout << ' ' << vi;
        std::cout << '\n';
    }
    return 0;
}

#line 1 "verify/lc_graph/lc_scc.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/scc"

#include <bits/stdc++.h>

#line 2 "graph/graph_template.hpp"

#line 4 "graph/graph_template.hpp"
template <class T> struct Edge {
    int from, to;
    T cost;
    int id;

    Edge() = default;
    Edge(int from, int to, T cost = 1, int id = -1) : from(from), to(to), cost(cost), id(id) {}

    friend std::ostream &operator<<(std::ostream &os, const Edge<T> &e) {
        // output format: "{ id : from -> to, cost }"
        return os << "{ " << e.id << " : " << e.from << " -> " << e.to << ", " << e.cost << " }";
    }
};

template <class T> using Edges = std::vector<Edge<T>>;
template <class T> using Graph = std::vector<std::vector<Edge<T>>>;
#line 2 "graph/read_graph.hpp"

#line 4 "graph/read_graph.hpp"

template <class T> Graph<T> read_graph(const int n, const int m, const bool weight = false, const bool directed = false, const int offset = 1) {
    Graph<T> g(n);
    for (int i = 0; i < m; i++) {
        int a, b;
        std::cin >> a >> b;
        a -= offset, b -= offset;
        if (weight) {
            T c;
            std::cin >> c;
            if (!directed) g[b].push_back(Edge(b, a, c, i));
            g[a].push_back(Edge(a, b, c, i));
        } else {
            // c = 1
            if (!directed) g[b].push_back(Edge(b, a, T(1), i));
            g[a].push_back(Edge(a, b, T(1), i));
        }
    }
    return g;
}

template <class T> Graph<T> read_parent(const int n, const bool weight = false, const bool directed = false, const int offset = 1) {
    Graph<T> g(n);
    for (int i = 1; i < n; i++) {
        int p;
        std::cin >> p;
        p -= offset;
        if (weight) {
            T c;
            std::cin >> c;
            if (!directed) g[i].push_back(Edge(i, p, c, i - 1));
            g[p].push_back(Edge(p, i, c, i - 1));
        } else {
            // c = 1
            if (!directed) g[i].push_back(Edge(i, p, T(1), i - 1));
            g[p].push_back(Edge(p, i, T(1), i - 1));
        }
    }
    return g;
}

std::tuple<Graph<int>, std::vector<std::vector<int>>, std::vector<std::pair<int, int>>> read_grid(const int h, const int w, std::string rel = ".#") {
    std::vector<std::string> s(h);
    std::vector id(h, std::vector<int>(w, -1));
    std::vector<std::pair<int, int>> loc;
    int n = 0;
    for (int i = 0; i < h; i++) {
        std::cin >> s[i];
        for (int j = 0; j < w; j++) {
            if (s[i][j] == rel[1]) {
                id[i][j] = n++;
                loc.emplace_back(i, j);
            }
        }
    }
    int m = 0;
    Graph<int> g(n);
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            if (s[i][j] == rel[1]) {
                if (i + 1 < h and s[i + 1][j] == rel[1]) {
                    g[id[i][j]].push_back(Edge(id[i][j], id[i + 1][j], 1, m));
                    g[id[i + 1][j]].push_back(Edge(id[i + 1][j], id[i][j], 1, m++));
                }
                if (j + 1 < w and s[i][j + 1] == rel[1]) {
                    g[id[i][j]].push_back(Edge(id[i][j], id[i][j + 1], 1, m));
                    g[id[i][j + 1]].push_back(Edge(id[i][j + 1], id[i][j], 1, m++));
                }
            }
        }
    }
    return {g, id, loc};
}
#line 2 "graph/strongly_connected_component.hpp"

#line 4 "graph/strongly_connected_component.hpp"

template <class T> std::vector<std::vector<int>> strongly_connected_component(Graph<T>& g) {
    int n = int(g.size());
    int now_ord = 0, group_num = 0;
    std::vector<int> visited, low(n), ord(n, -1), ids(n);
    visited.reserve(n);
    auto dfs = [&](auto f, int cur) -> void {
        low[cur] = ord[cur] = now_ord++;
        visited.push_back(cur);
        for (auto& e : g[cur]) {
            if (ord[e.to] == -1) {
                f(f, e.to);
                low[cur] = std::min(low[cur], low[e.to]);
            } else {
                low[cur] = std::min(low[cur], ord[e.to]);
            }
        }
        if (low[cur] == ord[cur]) {
            while (true) {
                int u = visited.back();
                visited.pop_back();
                ord[u] = n;
                ids[u] = group_num;
                if (u == cur) break;
            }
            group_num++;
        }
    };
    for (int i = 0; i < n; i++) {
        if (ord[i] == -1) dfs(dfs, i);
    }
    for (auto& x : ids) {
        x = group_num - 1 - x;
    }
    std::vector<int> counts(group_num);
    for (auto& x : ids) counts[x]++;
    std::vector<std::vector<int>> groups(group_num);
    for (int i = 0; i < group_num; i++) {
        groups[i].reserve(counts[i]);
    }
    for (int i = 0; i < n; i++) {
        groups[ids[i]].push_back(i);
    }
    return groups;
}
#line 8 "verify/lc_graph/lc_scc.test.cpp"

int main() {
    int N, M;
    std::cin >> N >> M;
    auto G = read_graph<int>(N, M, false, true, 0);
    auto scc = strongly_connected_component(G);
    std::cout << scc.size() << '\n';
    for (auto& vec : scc) {
        std::cout << vec.size();
        for (auto& vi : vec) std::cout << ' ' << vi;
        std::cout << '\n';
    }
    return 0;
}