kyopro-lib

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:x: Decompose forest
(Mylib/Graph/TreeUtils/forest.cpp)

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Code

#pragma once
#include <algorithm>
#include <utility>
#include <vector>
#include "Mylib/Graph/Template/graph.cpp"

namespace haar_lib {
  template <typename T>
  class forest {
    std::vector<tree<T>> trees_;
    std::vector<int> tree_id_, vertex_id_;
    std::vector<std::vector<int>> rid_;

  public:
    forest() {}
    forest(const graph<T> &g) {
      const int N = g.size();

      tree_id_.resize(N);
      vertex_id_.resize(N);

      std::vector<bool> check(N);

      auto dfs =
          [&](auto &dfs, int cur, std::vector<int> &vertices, std::vector<edge<T>> &edges) -> void {
        check[cur] = true;
        vertices.push_back(cur);

        for (auto &e : g[cur]) {
          edges.push_back(e);

          if (not check[e.to]) {
            dfs(dfs, e.to, vertices, edges);
          }
        }
      };

      for (int i = 0; i < N; ++i) {
        if (not check[i]) {
          std::vector<int> vertices;
          std::vector<edge<T>> edges;
          dfs(dfs, i, vertices, edges);

          const int m = vertices.size();
          const int k = trees_.size();

          rid_.emplace_back(m);

          for (int i = 0; i < (int) vertices.size(); ++i) {
            tree_id_[vertices[i]]   = k;
            vertex_id_[vertices[i]] = i;
            rid_[k][i]              = vertices[i];
          }

          trees_.push_back(m);

          for (auto &e : edges) {
            trees_[k].add_edge(vertex_id_[e.from], vertex_id_[e.to], e.cost);
          }
        }
      }
    }

    const auto &trees() const { return trees_; }
    auto id(int i) const { return std::make_pair(tree_id_[i], vertex_id_[i]); }
    int tree_id(int i) const { return tree_id_[i]; }
    int vertex_id(int i) const { return vertex_id_[i]; }
    int rid(int t, int u) const { return rid_[t][u]; }

    bool in_same_tree(int i, int j) const {
      return tree_id_[i] == tree_id_[j];
    }
  };
}  // namespace haar_lib
#line 2 "Mylib/Graph/TreeUtils/forest.cpp"
#include <algorithm>
#include <utility>
#include <vector>
#line 2 "Mylib/Graph/Template/graph.cpp"
#include <iostream>
#line 4 "Mylib/Graph/Template/graph.cpp"

namespace haar_lib {
  template <typename T>
  struct edge {
    int from, to;
    T cost;
    int index = -1;
    edge() {}
    edge(int from, int to, T cost) : from(from), to(to), cost(cost) {}
    edge(int from, int to, T cost, int index) : from(from), to(to), cost(cost), index(index) {}
  };

  template <typename T>
  struct graph {
    using weight_type = T;
    using edge_type   = edge<T>;

    std::vector<std::vector<edge<T>>> data;

    auto& operator[](size_t i) { return data[i]; }
    const auto& operator[](size_t i) const { return data[i]; }

    auto begin() const { return data.begin(); }
    auto end() const { return data.end(); }

    graph() {}
    graph(int N) : data(N) {}

    bool empty() const { return data.empty(); }
    int size() const { return data.size(); }

    void add_edge(int i, int j, T w, int index = -1) {
      data[i].emplace_back(i, j, w, index);
    }

    void add_undirected(int i, int j, T w, int index = -1) {
      add_edge(i, j, w, index);
      add_edge(j, i, w, index);
    }

    template <size_t I, bool DIRECTED = true, bool WEIGHTED = true>
    void read(int M) {
      for (int i = 0; i < M; ++i) {
        int u, v;
        std::cin >> u >> v;
        u -= I;
        v -= I;
        T w = 1;
        if (WEIGHTED) std::cin >> w;
        if (DIRECTED)
          add_edge(u, v, w, i);
        else
          add_undirected(u, v, w, i);
      }
    }
  };

  template <typename T>
  using tree = graph<T>;
}  // namespace haar_lib
#line 6 "Mylib/Graph/TreeUtils/forest.cpp"

namespace haar_lib {
  template <typename T>
  class forest {
    std::vector<tree<T>> trees_;
    std::vector<int> tree_id_, vertex_id_;
    std::vector<std::vector<int>> rid_;

  public:
    forest() {}
    forest(const graph<T> &g) {
      const int N = g.size();

      tree_id_.resize(N);
      vertex_id_.resize(N);

      std::vector<bool> check(N);

      auto dfs =
          [&](auto &dfs, int cur, std::vector<int> &vertices, std::vector<edge<T>> &edges) -> void {
        check[cur] = true;
        vertices.push_back(cur);

        for (auto &e : g[cur]) {
          edges.push_back(e);

          if (not check[e.to]) {
            dfs(dfs, e.to, vertices, edges);
          }
        }
      };

      for (int i = 0; i < N; ++i) {
        if (not check[i]) {
          std::vector<int> vertices;
          std::vector<edge<T>> edges;
          dfs(dfs, i, vertices, edges);

          const int m = vertices.size();
          const int k = trees_.size();

          rid_.emplace_back(m);

          for (int i = 0; i < (int) vertices.size(); ++i) {
            tree_id_[vertices[i]]   = k;
            vertex_id_[vertices[i]] = i;
            rid_[k][i]              = vertices[i];
          }

          trees_.push_back(m);

          for (auto &e : edges) {
            trees_[k].add_edge(vertex_id_[e.from], vertex_id_[e.to], e.cost);
          }
        }
      }
    }

    const auto &trees() const { return trees_; }
    auto id(int i) const { return std::make_pair(tree_id_[i], vertex_id_[i]); }
    int tree_id(int i) const { return tree_id_[i]; }
    int vertex_id(int i) const { return vertex_id_[i]; }
    int rid(int t, int u) const { return rid_[t][u]; }

    bool in_same_tree(int i, int j) const {
      return tree_id_[i] == tree_id_[j];
    }
  };
}  // namespace haar_lib
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