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/* -*- C++ -*-
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* lemon/floyd_warshall.h - Part of LEMON, a generic C++ optimization library
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*
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* Copyright (C) 2006 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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* (Egervary Research Group on Combinatorial Optimization, EGRES).
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*
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* Permission to use, modify and distribute this software is granted
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* provided that this copyright notice appears in all copies. For
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* precise terms see the accompanying LICENSE file.
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*
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* This software is provided "AS IS" with no warranty of any kind,
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* express or implied, and with no claim as to its suitability for any
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* purpose.
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*
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*/
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#ifndef LEMON_FLOYD_WARSHALL_H
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#define LEMON_FLOYD_WARSHALL_H
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///\ingroup flowalgs
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/// \file
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/// \brief FloydWarshall algorithm.
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///
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#include <lemon/list_graph.h>
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#include <lemon/graph_utils.h>
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#include <lemon/invalid.h>
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#include <lemon/error.h>
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#include <lemon/matrix_maps.h>
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#include <lemon/maps.h>
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#include <limits>
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namespace lemon {
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/// \brief Default OperationTraits for the FloydWarshall algorithm class.
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///
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/// It defines all computational operations and constants which are
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/// used in the Floyd-Warshall algorithm. The default implementation
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/// is based on the numeric_limits class. If the numeric type does not
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/// have infinity value then the maximum value is used as extremal
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/// infinity value.
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template <
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typename Value,
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bool has_infinity = std::numeric_limits<Value>::has_infinity>
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struct FloydWarshallDefaultOperationTraits {
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/// \brief Gives back the zero value of the type.
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static Value zero() {
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return static_cast<Value>(0);
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}
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/// \brief Gives back the positive infinity value of the type.
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static Value infinity() {
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return std::numeric_limits<Value>::infinity();
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}
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/// \brief Gives back the sum of the given two elements.
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static Value plus(const Value& left, const Value& right) {
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return left + right;
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}
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/// \brief Gives back true only if the first value less than the second.
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static bool less(const Value& left, const Value& right) {
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return left < right;
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}
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};
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template <typename Value>
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struct FloydWarshallDefaultOperationTraits<Value, false> {
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static Value zero() {
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return static_cast<Value>(0);
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}
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static Value infinity() {
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return std::numeric_limits<Value>::max();
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}
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static Value plus(const Value& left, const Value& right) {
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if (left == infinity() || right == infinity()) return infinity();
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return left + right;
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}
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static bool less(const Value& left, const Value& right) {
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return left < right;
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}
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};
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/// \brief Default traits class of FloydWarshall class.
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///
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/// Default traits class of FloydWarshall class.
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/// \param _Graph Graph type.
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/// \param _LegthMap Type of length map.
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template<class _Graph, class _LengthMap>
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struct FloydWarshallDefaultTraits {
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/// The graph type the algorithm runs on.
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typedef _Graph Graph;
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/// \brief The type of the map that stores the edge lengths.
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///
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/// The type of the map that stores the edge lengths.
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/// It must meet the \ref concept::ReadMap "ReadMap" concept.
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typedef _LengthMap LengthMap;
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// The type of the length of the edges.
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typedef typename _LengthMap::Value Value;
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/// \brief Operation traits for floyd-warshall algorithm.
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///
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/// It defines the infinity type on the given Value type
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/// and the used operation.
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/// \see FloydWarshallDefaultOperationTraits
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typedef FloydWarshallDefaultOperationTraits<Value> OperationTraits;
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/// \brief The type of the matrix map that stores the last edges of the
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/// shortest paths.
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///
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/// The type of the map that stores the last edges of the shortest paths.
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/// It must be a matrix map with \c Graph::Edge value type.
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///
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typedef DynamicMatrixMap<Graph, typename Graph::Node,
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typename Graph::Edge> PredMap;
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/// \brief Instantiates a PredMap.
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///
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/// This function instantiates a \ref PredMap.
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/// \param G is the graph, to which we would like to define the PredMap.
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/// \todo The graph alone may be insufficient for the initialization
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static PredMap *createPredMap(const _Graph& graph) {
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return new PredMap(graph);
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}
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/// \brief The type of the map that stores the dists of the nodes.
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///
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/// The type of the map that stores the dists of the nodes.
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/// It must meet the \ref concept::WriteMatrixMap "WriteMatrixMap" concept.
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///
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typedef DynamicMatrixMap<Graph, typename Graph::Node, Value> DistMap;
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/// \brief Instantiates a DistMap.
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///
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/// This function instantiates a \ref DistMap.
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/// \param G is the graph, to which we would like to define the
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/// \ref DistMap
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static DistMap *createDistMap(const _Graph& graph) {
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return new DistMap(graph);
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}
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};
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/// \brief %FloydWarshall algorithm class.
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///
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/// \ingroup flowalgs
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/// This class provides an efficient implementation of \c Floyd-Warshall
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/// algorithm. The edge lengths are passed to the algorithm using a
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/// \ref concept::ReadMap "ReadMap", so it is easy to change it to any
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/// kind of length.
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///
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/// The algorithm solves the shortest path problem for each pair
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/// of node when the edges can have negative length but the graph should
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/// not contain cycles with negative sum of length. If we can assume
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/// that all edge is non-negative in the graph then the dijkstra algorithm
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/// should be used from each node rather and if the graph is sparse and
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/// there are negative circles then the johnson algorithm.
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///
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/// The complexity of this algorithm is O(n^3 + e).
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///
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/// The type of the length is determined by the
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/// \ref concept::ReadMap::Value "Value" of the length map.
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///
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/// \param _Graph The graph type the algorithm runs on. The default value
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/// is \ref ListGraph. The value of _Graph is not used directly by
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/// FloydWarshall, it is only passed to \ref FloydWarshallDefaultTraits.
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/// \param _LengthMap This read-only EdgeMap determines the lengths of the
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/// edges. It is read once for each edge, so the map may involve in
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/// relatively time consuming process to compute the edge length if
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/// it is necessary. The default map type is \ref
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/// concept::StaticGraph::EdgeMap "Graph::EdgeMap<int>". The value
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/// of _LengthMap is not used directly by FloydWarshall, it is only passed
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/// to \ref FloydWarshallDefaultTraits. \param _Traits Traits class to set
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/// various data types used by the algorithm. The default traits
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/// class is \ref FloydWarshallDefaultTraits
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/// "FloydWarshallDefaultTraits<_Graph,_LengthMap>". See \ref
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/// FloydWarshallDefaultTraits for the documentation of a FloydWarshall
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/// traits class.
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///
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/// \author Balazs Dezso
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#ifdef DOXYGEN
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template <typename _Graph, typename _LengthMap typename _Traits >
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#else
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template <typename _Graph=ListGraph,
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typename _LengthMap=typename _Graph::template EdgeMap<int>,
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typename _Traits=FloydWarshallDefaultTraits<_Graph,_LengthMap> >
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#endif
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class FloydWarshall {
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public:
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/// \brief \ref Exception for uninitialized parameters.
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///
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/// This error represents problems in the initialization
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/// of the parameters of the algorithms.
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class UninitializedParameter : public lemon::UninitializedParameter {
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public:
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virtual const char* exceptionName() const {
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return "lemon::FloydWarshall::UninitializedParameter";
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}
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};
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typedef _Traits Traits;
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///The type of the underlying graph.
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typedef typename _Traits::Graph Graph;
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typedef typename Graph::Node Node;
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typedef typename Graph::NodeIt NodeIt;
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typedef typename Graph::Edge Edge;
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typedef typename Graph::EdgeIt EdgeIt;
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/// \brief The type of the length of the edges.
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typedef typename _Traits::LengthMap::Value Value;
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/// \brief The type of the map that stores the edge lengths.
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typedef typename _Traits::LengthMap LengthMap;
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/// \brief The type of the map that stores the last
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/// edges of the shortest paths. The type of the PredMap
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/// is a matrix map for Edges
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typedef typename _Traits::PredMap PredMap;
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/// \brief The type of the map that stores the dists of the nodes.
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/// The type of the DistMap is a matrix map for Values
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typedef typename _Traits::DistMap DistMap;
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/// \brief The operation traits.
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typedef typename _Traits::OperationTraits OperationTraits;
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private:
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/// Pointer to the underlying graph.
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const Graph *graph;
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/// Pointer to the length map
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const LengthMap *length;
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///Pointer to the map of predecessors edges.
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PredMap *_pred;
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///Indicates if \ref _pred is locally allocated (\c true) or not.
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bool local_pred;
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///Pointer to the map of distances.
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DistMap *_dist;
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///Indicates if \ref _dist is locally allocated (\c true) or not.
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bool local_dist;
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/// Creates the maps if necessary.
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void create_maps() {
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if(!_pred) {
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local_pred = true;
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_pred = Traits::createPredMap(*graph);
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}
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if(!_dist) {
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local_dist = true;
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_dist = Traits::createDistMap(*graph);
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}
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}
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public :
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/// \name Named template parameters
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///@{
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template <class T>
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struct DefPredMapTraits : public Traits {
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typedef T PredMap;
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static PredMap *createPredMap(const Graph& graph) {
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throw UninitializedParameter();
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}
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};
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/// \brief \ref named-templ-param "Named parameter" for setting PredMap
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/// type
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/// \ref named-templ-param "Named parameter" for setting PredMap type
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///
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template <class T>
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struct DefPredMap
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: public FloydWarshall< Graph, LengthMap, DefPredMapTraits<T> > {
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typedef FloydWarshall< Graph, LengthMap, DefPredMapTraits<T> > Create;
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};
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template <class T>
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struct DefDistMapTraits : public Traits {
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typedef T DistMap;
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static DistMap *createDistMap(const Graph& graph) {
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throw UninitializedParameter();
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}
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};
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/// \brief \ref named-templ-param "Named parameter" for setting DistMap
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/// type
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///
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/// \ref named-templ-param "Named parameter" for setting DistMap type
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///
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template <class T>
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struct DefDistMap
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: public FloydWarshall< Graph, LengthMap, DefDistMapTraits<T> > {
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typedef FloydWarshall< Graph, LengthMap, DefDistMapTraits<T> > Create;
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};
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template <class T>
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struct DefOperationTraitsTraits : public Traits {
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typedef T OperationTraits;
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};
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/// \brief \ref named-templ-param "Named parameter" for setting
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/// OperationTraits type
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///
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/// \ref named-templ-param "Named parameter" for setting PredMap type
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template <class T>
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struct DefOperationTraits
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: public FloydWarshall< Graph, LengthMap, DefOperationTraitsTraits<T> > {
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typedef FloydWarshall< Graph, LengthMap, DefOperationTraitsTraits<T> >
|
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|
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Create;
|
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|
308 |
};
|
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|
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|
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|
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///@}
|
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|
311 |
|
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|
312 |
protected:
|
deba@1710
|
313 |
|
deba@1710
|
314 |
FloydWarshall() {}
|
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|
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|
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|
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public:
|
deba@1710
|
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|
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|
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typedef FloydWarshall Create;
|
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|
319 |
|
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|
320 |
/// \brief Constructor.
|
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|
321 |
///
|
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|
322 |
/// \param _graph the graph the algorithm will run on.
|
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|
323 |
/// \param _length the length map used by the algorithm.
|
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|
324 |
FloydWarshall(const Graph& _graph, const LengthMap& _length) :
|
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|
325 |
graph(&_graph), length(&_length),
|
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|
326 |
_pred(0), local_pred(false),
|
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_dist(0), local_dist(false) {}
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|
328 |
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|
329 |
///Destructor.
|
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|
330 |
~FloydWarshall() {
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331 |
if(local_pred) delete _pred;
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|
332 |
if(local_dist) delete _dist;
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|
333 |
}
|
deba@1699
|
334 |
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|
335 |
/// \brief Sets the length map.
|
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336 |
///
|
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/// Sets the length map.
|
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/// \return \c (*this)
|
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|
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FloydWarshall &lengthMap(const LengthMap &m) {
|
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|
340 |
length = &m;
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|
341 |
return *this;
|
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}
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|
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deba@1699
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/// \brief Sets the map storing the predecessor edges.
|
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345 |
///
|
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/// Sets the map storing the predecessor edges.
|
deba@1699
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/// If you don't use this function before calling \ref run(),
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|
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/// it will allocate one. The destuctor deallocates this
|
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349 |
/// automatically allocated map, of course.
|
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/// \return \c (*this)
|
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FloydWarshall &predMap(PredMap &m) {
|
deba@1699
|
352 |
if(local_pred) {
|
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|
353 |
delete _pred;
|
deba@1699
|
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local_pred=false;
|
deba@1699
|
355 |
}
|
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|
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_pred = &m;
|
deba@1699
|
357 |
return *this;
|
deba@1699
|
358 |
}
|
deba@1699
|
359 |
|
deba@1699
|
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/// \brief Sets the map storing the distances calculated by the algorithm.
|
deba@1699
|
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///
|
deba@1699
|
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/// Sets the map storing the distances calculated by the algorithm.
|
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|
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/// If you don't use this function before calling \ref run(),
|
deba@1699
|
364 |
/// it will allocate one. The destuctor deallocates this
|
deba@1699
|
365 |
/// automatically allocated map, of course.
|
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|
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/// \return \c (*this)
|
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|
367 |
FloydWarshall &distMap(DistMap &m) {
|
deba@1699
|
368 |
if(local_dist) {
|
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|
369 |
delete _dist;
|
deba@1699
|
370 |
local_dist=false;
|
deba@1699
|
371 |
}
|
deba@1699
|
372 |
_dist = &m;
|
deba@1699
|
373 |
return *this;
|
deba@1699
|
374 |
}
|
deba@1699
|
375 |
|
deba@1699
|
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///\name Execution control
|
deba@1699
|
377 |
/// The simplest way to execute the algorithm is to use
|
deba@1699
|
378 |
/// one of the member functions called \c run(...).
|
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|
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/// \n
|
deba@1699
|
380 |
/// If you need more control on the execution,
|
deba@1699
|
381 |
/// Finally \ref start() will perform the actual path
|
deba@1699
|
382 |
/// computation.
|
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|
383 |
|
deba@1699
|
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///@{
|
deba@1699
|
385 |
|
deba@1699
|
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/// \brief Initializes the internal data structures.
|
deba@1699
|
387 |
///
|
deba@1699
|
388 |
/// Initializes the internal data structures.
|
deba@1699
|
389 |
void init() {
|
deba@1699
|
390 |
create_maps();
|
deba@1699
|
391 |
for (NodeIt it(*graph); it != INVALID; ++it) {
|
deba@1699
|
392 |
for (NodeIt jt(*graph); jt != INVALID; ++jt) {
|
deba@1699
|
393 |
_pred->set(it, jt, INVALID);
|
deba@1741
|
394 |
_dist->set(it, jt, OperationTraits::infinity());
|
deba@1699
|
395 |
}
|
deba@1741
|
396 |
_dist->set(it, it, OperationTraits::zero());
|
deba@1699
|
397 |
}
|
deba@1699
|
398 |
for (EdgeIt it(*graph); it != INVALID; ++it) {
|
deba@1699
|
399 |
Node source = graph->source(it);
|
deba@1699
|
400 |
Node target = graph->target(it);
|
deba@1699
|
401 |
if (OperationTraits::less((*length)[it], (*_dist)(source, target))) {
|
deba@1699
|
402 |
_dist->set(source, target, (*length)[it]);
|
deba@1699
|
403 |
_pred->set(source, target, it);
|
deba@1699
|
404 |
}
|
deba@1699
|
405 |
}
|
deba@1699
|
406 |
}
|
deba@1699
|
407 |
|
deba@1699
|
408 |
/// \brief Executes the algorithm.
|
deba@1699
|
409 |
///
|
deba@1699
|
410 |
/// This method runs the %FloydWarshall algorithm in order to compute
|
deba@1699
|
411 |
/// the shortest path to each node pairs. The algorithm
|
deba@1699
|
412 |
/// computes
|
deba@1699
|
413 |
/// - The shortest path tree for each node.
|
deba@1699
|
414 |
/// - The distance between each node pairs.
|
deba@1699
|
415 |
void start() {
|
deba@1699
|
416 |
for (NodeIt kt(*graph); kt != INVALID; ++kt) {
|
deba@1699
|
417 |
for (NodeIt it(*graph); it != INVALID; ++it) {
|
deba@1699
|
418 |
for (NodeIt jt(*graph); jt != INVALID; ++jt) {
|
deba@1699
|
419 |
Value relaxed = OperationTraits::plus((*_dist)(it, kt),
|
deba@1699
|
420 |
(*_dist)(kt, jt));
|
deba@1699
|
421 |
if (OperationTraits::less(relaxed, (*_dist)(it, jt))) {
|
deba@1699
|
422 |
_dist->set(it, jt, relaxed);
|
deba@1699
|
423 |
_pred->set(it, jt, (*_pred)(kt, jt));
|
deba@1699
|
424 |
}
|
deba@1699
|
425 |
}
|
deba@1699
|
426 |
}
|
deba@1699
|
427 |
}
|
deba@1699
|
428 |
}
|
deba@1741
|
429 |
|
deba@1754
|
430 |
/// \brief Executes the algorithm and checks the negative cycles.
|
deba@1741
|
431 |
///
|
deba@1741
|
432 |
/// This method runs the %FloydWarshall algorithm in order to compute
|
deba@1754
|
433 |
/// the shortest path to each node pairs. If there is a negative cycle
|
deba@1741
|
434 |
/// in the graph it gives back false.
|
deba@1741
|
435 |
/// The algorithm computes
|
deba@1741
|
436 |
/// - The shortest path tree for each node.
|
deba@1741
|
437 |
/// - The distance between each node pairs.
|
deba@1741
|
438 |
bool checkedStart() {
|
deba@1741
|
439 |
start();
|
deba@1741
|
440 |
for (NodeIt it(*graph); it != INVALID; ++it) {
|
deba@1741
|
441 |
if (OperationTraits::less((*dist)(it, it), OperationTraits::zero())) {
|
deba@1741
|
442 |
return false;
|
deba@1741
|
443 |
}
|
deba@1741
|
444 |
}
|
deba@1741
|
445 |
return true;
|
deba@1741
|
446 |
}
|
deba@1699
|
447 |
|
deba@1699
|
448 |
/// \brief Runs %FloydWarshall algorithm.
|
deba@1699
|
449 |
///
|
deba@1699
|
450 |
/// This method runs the %FloydWarshall algorithm from a each node
|
deba@1699
|
451 |
/// in order to compute the shortest path to each node pairs.
|
deba@1699
|
452 |
/// The algorithm computes
|
deba@1699
|
453 |
/// - The shortest path tree for each node.
|
deba@1699
|
454 |
/// - The distance between each node pairs.
|
deba@1699
|
455 |
///
|
deba@1699
|
456 |
/// \note d.run(s) is just a shortcut of the following code.
|
deba@1699
|
457 |
/// \code
|
deba@1699
|
458 |
/// d.init();
|
deba@1699
|
459 |
/// d.start();
|
deba@1699
|
460 |
/// \endcode
|
deba@1699
|
461 |
void run() {
|
deba@1699
|
462 |
init();
|
deba@1699
|
463 |
start();
|
deba@1699
|
464 |
}
|
deba@1699
|
465 |
|
deba@1699
|
466 |
///@}
|
deba@1699
|
467 |
|
deba@1699
|
468 |
/// \name Query Functions
|
deba@1699
|
469 |
/// The result of the %FloydWarshall algorithm can be obtained using these
|
deba@1699
|
470 |
/// functions.\n
|
deba@1699
|
471 |
/// Before the use of these functions,
|
deba@1699
|
472 |
/// either run() or start() must be called.
|
deba@1699
|
473 |
|
deba@1699
|
474 |
///@{
|
deba@1699
|
475 |
|
deba@1699
|
476 |
/// \brief Copies the shortest path to \c t into \c p
|
deba@1699
|
477 |
///
|
deba@1699
|
478 |
/// This function copies the shortest path to \c t into \c p.
|
deba@1699
|
479 |
/// If it \c t is a source itself or unreachable, then it does not
|
deba@1699
|
480 |
/// alter \c p.
|
deba@1699
|
481 |
/// \return Returns \c true if a path to \c t was actually copied to \c p,
|
deba@1699
|
482 |
/// \c false otherwise.
|
deba@1699
|
483 |
/// \sa DirPath
|
deba@1699
|
484 |
template <typename Path>
|
deba@1699
|
485 |
bool getPath(Path &p, Node source, Node target) {
|
deba@1699
|
486 |
if (connected(source, target)) {
|
deba@1699
|
487 |
p.clear();
|
deba@1699
|
488 |
typename Path::Builder b(target);
|
deba@1763
|
489 |
for(b.setStartNode(target); predEdge(source, target) != INVALID;
|
deba@1699
|
490 |
target = predNode(target)) {
|
deba@1763
|
491 |
b.pushFront(predEdge(source, target));
|
deba@1699
|
492 |
}
|
deba@1699
|
493 |
b.commit();
|
deba@1699
|
494 |
return true;
|
deba@1699
|
495 |
}
|
deba@1699
|
496 |
return false;
|
deba@1699
|
497 |
}
|
deba@1699
|
498 |
|
deba@1699
|
499 |
/// \brief The distance between two nodes.
|
deba@1699
|
500 |
///
|
deba@1699
|
501 |
/// Returns the distance between two nodes.
|
deba@1699
|
502 |
/// \pre \ref run() must be called before using this function.
|
deba@1699
|
503 |
/// \warning If node \c v in unreachable from the root the return value
|
deba@1699
|
504 |
/// of this funcion is undefined.
|
deba@1699
|
505 |
Value dist(Node source, Node target) const {
|
deba@1699
|
506 |
return (*_dist)(source, target);
|
deba@1699
|
507 |
}
|
deba@1699
|
508 |
|
deba@1699
|
509 |
/// \brief Returns the 'previous edge' of the shortest path tree.
|
deba@1699
|
510 |
///
|
deba@1699
|
511 |
/// For the node \c node it returns the 'previous edge' of the shortest
|
deba@1699
|
512 |
/// path tree to direction of the node \c root
|
deba@1699
|
513 |
/// i.e. it returns the last edge of a shortest path from the node \c root
|
deba@1699
|
514 |
/// to \c node. It is \ref INVALID if \c node is unreachable from the root
|
deba@1699
|
515 |
/// or if \c node=root. The shortest path tree used here is equal to the
|
deba@1699
|
516 |
/// shortest path tree used in \ref predNode().
|
deba@1699
|
517 |
/// \pre \ref run() must be called before using this function.
|
deba@1763
|
518 |
Edge predEdge(Node root, Node node) const {
|
deba@1699
|
519 |
return (*_pred)(root, node);
|
deba@1699
|
520 |
}
|
deba@1699
|
521 |
|
deba@1699
|
522 |
/// \brief Returns the 'previous node' of the shortest path tree.
|
deba@1699
|
523 |
///
|
deba@1699
|
524 |
/// For a node \c node it returns the 'previous node' of the shortest path
|
deba@1699
|
525 |
/// tree to direction of the node \c root, i.e. it returns the last but
|
deba@1699
|
526 |
/// one node from a shortest path from the \c root to \c node. It is
|
deba@1699
|
527 |
/// INVALID if \c node is unreachable from the root or if \c node=root.
|
deba@1699
|
528 |
/// The shortest path tree used here is equal to the
|
deba@1763
|
529 |
/// shortest path tree used in \ref predEdge().
|
deba@1699
|
530 |
/// \pre \ref run() must be called before using this function.
|
deba@1699
|
531 |
Node predNode(Node root, Node node) const {
|
deba@1699
|
532 |
return (*_pred)(root, node) == INVALID ?
|
deba@1699
|
533 |
INVALID : graph->source((*_pred)(root, node));
|
deba@1699
|
534 |
}
|
deba@1699
|
535 |
|
deba@1699
|
536 |
/// \brief Returns a reference to the matrix node map of distances.
|
deba@1699
|
537 |
///
|
deba@1699
|
538 |
/// Returns a reference to the matrix node map of distances.
|
deba@1699
|
539 |
///
|
deba@1699
|
540 |
/// \pre \ref run() must be called before using this function.
|
deba@1699
|
541 |
const DistMap &distMap() const { return *_dist;}
|
deba@1699
|
542 |
|
deba@1699
|
543 |
/// \brief Returns a reference to the shortest path tree map.
|
deba@1699
|
544 |
///
|
deba@1699
|
545 |
/// Returns a reference to the matrix node map of the edges of the
|
deba@1699
|
546 |
/// shortest path tree.
|
deba@1699
|
547 |
/// \pre \ref run() must be called before using this function.
|
deba@1699
|
548 |
const PredMap &predMap() const { return *_pred;}
|
deba@1699
|
549 |
|
deba@1699
|
550 |
/// \brief Checks if a node is reachable from the root.
|
deba@1699
|
551 |
///
|
deba@1699
|
552 |
/// Returns \c true if \c v is reachable from the root.
|
deba@1699
|
553 |
/// \pre \ref run() must be called before using this function.
|
deba@1699
|
554 |
///
|
deba@1699
|
555 |
bool connected(Node source, Node target) {
|
deba@1699
|
556 |
return (*_dist)(source, target) != OperationTraits::infinity();
|
deba@1699
|
557 |
}
|
deba@1699
|
558 |
|
deba@1699
|
559 |
///@}
|
deba@1699
|
560 |
};
|
deba@1699
|
561 |
|
deba@1699
|
562 |
} //END OF NAMESPACE LEMON
|
deba@1699
|
563 |
|
deba@1699
|
564 |
#endif
|
deba@1699
|
565 |
|