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Diffstat (limited to 'extern/quadriflow/3rd/lemon-1.3.1/lemon/nearest_neighbor_tsp.h')
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diff --git a/extern/quadriflow/3rd/lemon-1.3.1/lemon/nearest_neighbor_tsp.h b/extern/quadriflow/3rd/lemon-1.3.1/lemon/nearest_neighbor_tsp.h new file mode 100644 index 00000000000..065e145df08 --- /dev/null +++ b/extern/quadriflow/3rd/lemon-1.3.1/lemon/nearest_neighbor_tsp.h @@ -0,0 +1,238 @@ +/* -*- mode: C++; indent-tabs-mode: nil; -*- + * + * This file is a part of LEMON, a generic C++ optimization library. + * + * Copyright (C) 2003-2013 + * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport + * (Egervary Research Group on Combinatorial Optimization, EGRES). + * + * Permission to use, modify and distribute this software is granted + * provided that this copyright notice appears in all copies. For + * precise terms see the accompanying LICENSE file. + * + * This software is provided "AS IS" with no warranty of any kind, + * express or implied, and with no claim as to its suitability for any + * purpose. + * + */ + +#ifndef LEMON_NEAREST_NEIGHBOUR_TSP_H +#define LEMON_NEAREST_NEIGHBOUR_TSP_H + +/// \ingroup tsp +/// \file +/// \brief Nearest neighbor algorithm for symmetric TSP + +#include <deque> +#include <vector> +#include <limits> +#include <lemon/full_graph.h> +#include <lemon/maps.h> + +namespace lemon { + + /// \ingroup tsp + /// + /// \brief Nearest neighbor algorithm for symmetric TSP. + /// + /// NearestNeighborTsp implements the nearest neighbor heuristic for solving + /// symmetric \ref tsp "TSP". + /// + /// This is probably the simplest TSP heuristic. + /// It starts with a minimum cost edge and at each step, it connects the + /// nearest unvisited node to the current path. + /// Finally, it connects the two end points of the path to form a tour. + /// + /// This method runs in O(n<sup>2</sup>) time. + /// It quickly finds a relatively short tour for most TSP instances, + /// but it could also yield a really bad (or even the worst) solution + /// in special cases. + /// + /// \tparam CM Type of the cost map. + template <typename CM> + class NearestNeighborTsp + { + public: + + /// Type of the cost map + typedef CM CostMap; + /// Type of the edge costs + typedef typename CM::Value Cost; + + private: + + GRAPH_TYPEDEFS(FullGraph); + + const FullGraph &_gr; + const CostMap &_cost; + Cost _sum; + std::vector<Node> _path; + + public: + + /// \brief Constructor + /// + /// Constructor. + /// \param gr The \ref FullGraph "full graph" the algorithm runs on. + /// \param cost The cost map. + NearestNeighborTsp(const FullGraph &gr, const CostMap &cost) + : _gr(gr), _cost(cost) {} + + /// \name Execution Control + /// @{ + + /// \brief Runs the algorithm. + /// + /// This function runs the algorithm. + /// + /// \return The total cost of the found tour. + Cost run() { + _path.clear(); + if (_gr.nodeNum() == 0) { + return _sum = 0; + } + else if (_gr.nodeNum() == 1) { + _path.push_back(_gr(0)); + return _sum = 0; + } + + std::deque<Node> path_dq; + Edge min_edge1 = INVALID, + min_edge2 = INVALID; + + min_edge1 = mapMin(_gr, _cost); + Node n1 = _gr.u(min_edge1), + n2 = _gr.v(min_edge1); + path_dq.push_back(n1); + path_dq.push_back(n2); + + FullGraph::NodeMap<bool> used(_gr, false); + used[n1] = true; + used[n2] = true; + + min_edge1 = INVALID; + while (int(path_dq.size()) != _gr.nodeNum()) { + if (min_edge1 == INVALID) { + for (IncEdgeIt e(_gr, n1); e != INVALID; ++e) { + if (!used[_gr.runningNode(e)] && + (min_edge1 == INVALID || _cost[e] < _cost[min_edge1])) { + min_edge1 = e; + } + } + } + + if (min_edge2 == INVALID) { + for (IncEdgeIt e(_gr, n2); e != INVALID; ++e) { + if (!used[_gr.runningNode(e)] && + (min_edge2 == INVALID||_cost[e] < _cost[min_edge2])) { + min_edge2 = e; + } + } + } + + if (_cost[min_edge1] < _cost[min_edge2]) { + n1 = _gr.oppositeNode(n1, min_edge1); + path_dq.push_front(n1); + + used[n1] = true; + min_edge1 = INVALID; + + if (_gr.u(min_edge2) == n1 || _gr.v(min_edge2) == n1) + min_edge2 = INVALID; + } else { + n2 = _gr.oppositeNode(n2, min_edge2); + path_dq.push_back(n2); + + used[n2] = true; + min_edge2 = INVALID; + + if (_gr.u(min_edge1) == n2 || _gr.v(min_edge1) == n2) + min_edge1 = INVALID; + } + } + + n1 = path_dq.back(); + n2 = path_dq.front(); + _path.push_back(n2); + _sum = _cost[_gr.edge(n1, n2)]; + for (int i = 1; i < int(path_dq.size()); ++i) { + n1 = n2; + n2 = path_dq[i]; + _path.push_back(n2); + _sum += _cost[_gr.edge(n1, n2)]; + } + + return _sum; + } + + /// @} + + /// \name Query Functions + /// @{ + + /// \brief The total cost of the found tour. + /// + /// This function returns the total cost of the found tour. + /// + /// \pre run() must be called before using this function. + Cost tourCost() const { + return _sum; + } + + /// \brief Returns a const reference to the node sequence of the + /// found tour. + /// + /// This function returns a const reference to a vector + /// that stores the node sequence of the found tour. + /// + /// \pre run() must be called before using this function. + const std::vector<Node>& tourNodes() const { + return _path; + } + + /// \brief Gives back the node sequence of the found tour. + /// + /// This function copies the node sequence of the found tour into + /// an STL container through the given output iterator. The + /// <tt>value_type</tt> of the container must be <tt>FullGraph::Node</tt>. + /// For example, + /// \code + /// std::vector<FullGraph::Node> nodes(countNodes(graph)); + /// tsp.tourNodes(nodes.begin()); + /// \endcode + /// or + /// \code + /// std::list<FullGraph::Node> nodes; + /// tsp.tourNodes(std::back_inserter(nodes)); + /// \endcode + /// + /// \pre run() must be called before using this function. + template <typename Iterator> + void tourNodes(Iterator out) const { + std::copy(_path.begin(), _path.end(), out); + } + + /// \brief Gives back the found tour as a path. + /// + /// This function copies the found tour as a list of arcs/edges into + /// the given \ref lemon::concepts::Path "path structure". + /// + /// \pre run() must be called before using this function. + template <typename Path> + void tour(Path &path) const { + path.clear(); + for (int i = 0; i < int(_path.size()) - 1; ++i) { + path.addBack(_gr.arc(_path[i], _path[i+1])); + } + if (int(_path.size()) >= 2) { + path.addBack(_gr.arc(_path.back(), _path.front())); + } + } + + /// @} + + }; + +}; // namespace lemon + +#endif |