DFS.hpp

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// Copyright (c) 2017 Czech Technical University in Prague | Faculty of Information Technology. All rights reserved.
 
#pragma once
 
#include <functional>
#include <alib/vector>
#include <queue>
#include <alib/set>
#include <alib/map>
 
#include <common/ReconstructPath.hpp>
 
namespace graph {
 
namespace traverse {
 
class DFS {
// ---------------------------------------------------------------------------------------------------------------------
 
 public:
 
  template<
      typename TGraph,
      typename TNode,
      typename F = std::function<bool(const TNode &, const size_t &)>>
  static
  void
  run(const TGraph &graph,
      const TNode &start,
      F f_user = [](const TNode &, const size_t &) -> bool { return false; });
 
// ---------------------------------------------------------------------------------------------------------------------
 
  template<
      typename TGraph,
      typename TNode,
      typename F = std::function<void(const TNode &, const size_t &)>>
  static
  ext::vector<TNode>
  findPath(const TGraph &graph,
           const TNode &start,
           const TNode &goal,
           F f_user = [](const TNode &, const size_t &) {});
 
  template<typename TGraph, typename TNode>
  static
  ext::vector<TNode>
  findPathRegistration(const TGraph &graph,
                       const TNode &start,
                       const TNode &goal) {
    return findPath(graph, start, goal);
 
  }
 
// =====================================================================================================================
 
 private:
 
// ---------------------------------------------------------------------------------------------------------------------
 
  template<typename TNode>
  struct Data {
    ext::map<TNode, size_t> d; // distance
    ext::set<TNode> v; // visited
    ext::map<TNode, TNode> p; // parents
  };
 
// ---------------------------------------------------------------------------------------------------------------------
 
  template<typename TGraph, typename TNode, typename F1, typename F2>
  static
  ext::vector<TNode>
  impl(const TGraph &graph,
       const TNode &start,
       const TNode &goal,
       F1 f_user,
       F2 f_stop);
 
// ---------------------------------------------------------------------------------------------------------------------
 
  template<typename TGraph, typename TNode, typename F1, typename F2>
  static
  bool
  expansion(const TGraph &graph,
            DFS::Data<TNode> &data,
            const TNode &n,
            const TNode &p,
            F1 f_user,
            F2 f_stop);
 
// ---------------------------------------------------------------------------------------------------------------------
 
};
 
// =====================================================================================================================
 
template<typename TGraph, typename TNode, typename F>
void DFS::run(const TGraph &graph, const TNode &start, F f_user) {
  impl(graph, start, start, f_user, [](const TNode &) -> bool { return false; });
}
 
// ---------------------------------------------------------------------------------------------------------------------
 
template<typename TGraph, typename TNode, typename F>
ext::vector<TNode> DFS::findPath(const TGraph &graph, const TNode &start, const TNode &goal, F f_user) {
  return impl(graph, start, goal,
              [&](const TNode &n, const auto &d) -> bool {
                f_user(n, d);
                return false;
              },
              [&](const TNode &n) -> bool { return goal == n; });
}
 
// ---------------------------------------------------------------------------------------------------------------------
 
template<typename TGraph, typename TNode, typename F1, typename F2>
ext::vector<TNode> DFS::impl(const TGraph &graph,
                             const TNode &start,
                             const TNode &goal,
                             F1 f_user,
                             F2 f_stop) {
  Data<TNode> data;
 
  // Init search
  data.d[start] = -1;
 
  // Start DFS
  expansion(graph, data, start, start, f_user, f_stop);
 
  return common::ReconstructPath::reconstructPath(data.p, start, goal);
}
 
// ---------------------------------------------------------------------------------------------------------------------
 
template<typename TGraph, typename TNode, typename F1, typename F2>
bool
DFS::expansion(const TGraph &graph,
               DFS::Data<TNode> &data,
               const TNode &n,
               const TNode &p,
               F1 f_user,
               F2 f_stop) {
  if (data.v.find(n) != data.v.end()) return false;
 
  data.v.insert(n);
  data.p.insert_or_assign(n, p);
  data.d[n] = data.d[p] + 1;
 
  // Run user's function
  if (f_user(n, data.d[n])) {
    return true; // Stop algorithm
  }
 
  // Stop if reach the goal
  if (f_stop(n)) {
    return true; // Stop algorithm
  }
 
  for (const auto &i : graph.successors(n)) {
    bool stop = expansion(graph, data, i, n, f_user, f_stop);
 
    if (stop) {
      return true;
    }
  }
 
  return false;
}
 
 
// =====================================================================================================================
 
 
// ---------------------------------------------------------------------------------------------------------------------
 
} // namespace traverse
 
} // namespace graph