C++ Library for Competitive Programming
View the Project on GitHub emthrm/cp-library
/* * @title グラフ/lowlink(関節点) * * verification-helper: PROBLEM http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_A */ #include <algorithm> #include <iostream> #include <vector> #include "emthrm/graph/edge.hpp" #include "emthrm/graph/lowlink.hpp" int main() { int v, e; std::cin >> v >> e; std::vector<std::vector<emthrm::Edge<bool>>> graph(v); while (e--) { int s, t; std::cin >> s >> t; graph[s].emplace_back(s, t); graph[t].emplace_back(t, s); } std::vector<int> articulation_points = emthrm::Lowlink<bool>(graph).articulation_points; std::sort(articulation_points.begin(), articulation_points.end()); for (const int articulation_point : articulation_points) { std::cout << articulation_point << '\n'; } return 0; }
#line 1 "test/graph/lowlink.2.test.cpp" /* * @title グラフ/lowlink(関節点) * * verification-helper: PROBLEM http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_3_A */ #include <algorithm> #include <iostream> #include <vector> #line 1 "include/emthrm/graph/edge.hpp" /** * @title 辺 */ #ifndef EMTHRM_GRAPH_EDGE_HPP_ #define EMTHRM_GRAPH_EDGE_HPP_ #include <compare> namespace emthrm { template <typename CostType> struct Edge { CostType cost; int src, dst; explicit Edge(const int src, const int dst, const CostType cost = 0) : cost(cost), src(src), dst(dst) {} auto operator<=>(const Edge& x) const = default; }; } // namespace emthrm #endif // EMTHRM_GRAPH_EDGE_HPP_ #line 1 "include/emthrm/graph/lowlink.hpp" #line 6 "include/emthrm/graph/lowlink.hpp" #line 1 "include/emthrm/graph/edge.hpp" /** * @title 辺 */ #ifndef EMTHRM_GRAPH_EDGE_HPP_ #define EMTHRM_GRAPH_EDGE_HPP_ #include <compare> namespace emthrm { template <typename CostType> struct Edge { CostType cost; int src, dst; explicit Edge(const int src, const int dst, const CostType cost = 0) : cost(cost), src(src), dst(dst) {} auto operator<=>(const Edge& x) const = default; }; } // namespace emthrm #endif // EMTHRM_GRAPH_EDGE_HPP_ #line 8 "include/emthrm/graph/lowlink.hpp" namespace emthrm { template <typename CostType> struct Lowlink { std::vector<int> order, lowlink, articulation_points; std::vector<Edge<CostType>> bridges; const std::vector<std::vector<Edge<CostType>>> graph; explicit Lowlink(const std::vector<std::vector<Edge<CostType>>>& graph) : graph(graph) { const int n = graph.size(); order.assign(n, -1); lowlink.resize(n); int t = 0; for (int i = 0; i < n; ++i) { if (order[i] == -1) dfs(-1, i, &t); } } private: void dfs(const int par, const int ver, int* t) { order[ver] = lowlink[ver] = (*t)++; int num = 0; bool is_articulation_point = false; for (const Edge<CostType>& e : graph[ver]) { if (order[e.dst] == -1) { ++num; dfs(ver, e.dst, t); lowlink[ver] = std::min(lowlink[ver], lowlink[e.dst]); if (order[ver] <= lowlink[e.dst]) { is_articulation_point = true; if (order[ver] < lowlink[e.dst]) { bridges.emplace_back(std::min(ver, e.dst), std::max(ver, e.dst), e.cost); } } } else if (e.dst != par) { lowlink[ver] = std::min(lowlink[ver], order[e.dst]); } } if ((par == -1 && num >= 2) || (par != -1 && is_articulation_point)) { articulation_points.emplace_back(ver); } } }; } // namespace emthrm #line 13 "test/graph/lowlink.2.test.cpp" int main() { int v, e; std::cin >> v >> e; std::vector<std::vector<emthrm::Edge<bool>>> graph(v); while (e--) { int s, t; std::cin >> s >> t; graph[s].emplace_back(s, t); graph[t].emplace_back(t, s); } std::vector<int> articulation_points = emthrm::Lowlink<bool>(graph).articulation_points; std::sort(articulation_points.begin(), articulation_points.end()); for (const int articulation_point : articulation_points) { std::cout << articulation_point << '\n'; } return 0; }