CDirectedTree.h

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/* +---------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)               |
   |                          http://www.mrpt.org/                             |
   |                                                                           |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file        |
   | See: http://www.mrpt.org/Authors - All rights reserved.                   |
   | Released under BSD License. See details in http://www.mrpt.org/License    |
   +---------------------------------------------------------------------------+ */
#ifndef  MRPT_DIRECTED_TREE_H
#define  MRPT_DIRECTED_TREE_H

#include <mrpt/utils/utils_defs.h>
#include <list>

namespace mrpt
{
        namespace graphs
        {
                using mrpt::utils::TNodeID; //!< Make available this typedef in this namespace too

                /** A special kind of graph in the form of a tree with directed edges and optional edge annotations of templatized type "TYPE_EDGES".
                  *  The tree is represented by means of:
                  *             - \a root: The ID of the root node.
                  *             - \a edges_to_children: A map from node ID to all the edges to its children.
                  *
                  *  Note that nodes are *not* explicitly listed anywhere: their existence is only inferred from their ID numbers in the list
                  *  of edges in the \a edges_to_children data structure. If you want to include information for each node, derive from this class
                  *  and create a separate container for that data.
                  *
                  *  This class is less general than CDirectedGraph but more efficient to traverse (see \a visitDepthFirst and \a visitBreadthFirst).
                  *
                  *  If annotations in edges are not required, you can leave TYPE_EDGES to its default type "uint8_t".
                  *
                  *  Example of insertion of a new edge:
                  *  \code
                  *  typedef CDirectedTree<edge_t>  my_tree_t;
                  *  my_tree_t  tree;
                  *  TNodeID id_root = XXX;
                  *  TNodeID id_child = XXX;
                  *  my_tree_t::TListEdges & edges_of_root = tree.edges_to_children[id_root];
                  *  edges_of_root.push_back( my_tree_t::TEdgeInfo(id_child,false, edge_t(...) ) );
                  *  \endcode
                  *
                  *  \sa CDirectedGraph, CDijkstra, mrpt::graphs::CNetworkOfPoses
                 * \ingroup mrpt_graphs_grp
                  */
                template <class TYPE_EDGES = uint8_t>
                class CDirectedTree
                {
                public:
                        struct TEdgeInfo
                        {
                                TNodeID    id;      //!< The ID of the child node.
                                bool       reverse; //!< True if edge direction is child->parent, false if it's parent->child.
                                TYPE_EDGES data;    //!< User data for this edge.

                                /** Edge constructor from data */
                                TEdgeInfo(TNodeID child_id_, bool direction_child_to_parent=false, const TYPE_EDGES & edge_data = TYPE_EDGES() ) : id(child_id_), reverse(direction_child_to_parent), data(edge_data) { }
                        };

                        typedef std::list<TEdgeInfo>          TListEdges;
                        typedef std::map<TNodeID,TListEdges>  TMapNode2ListEdges;

                        /** @name Data
                            @{ */
                        TNodeID            root;               //!< The root of the tree
                        TMapNode2ListEdges edges_to_children;  //!< The edges of each node
                        /** @} */

                        /** @name Utilities
                            @{ */

                        /** Empty all edge data and set "root" to INVALID_NODEID */
                        void clear() { edges_to_children.clear(); root = INVALID_NODEID; }

                        /** Virtual base class for user-defined visitors */
                        struct Visitor
                        {
                                typedef CDirectedTree<TYPE_EDGES> tree_t;

                                /** Virtual method to be implemented by the user and which will be called during the visit to a graph with visitDepthFirst or visitBreadthFirst
                                  *  Specifically, the method will be called once for each <b>edge</b> in the tree.
                                  * \param parent [IN] The ID of the parent node.
                                  * \param edge_to_child [IN] The edge information from the parent to "edge_to_child.id"
                                  * \param depth_level [IN] The "depth level" of the child node "edge_to_child.id" (root node is at 0, its children are at 1, etc.).
                                  */
                                virtual void OnVisitNode( const TNodeID parent, const typename tree_t::TEdgeInfo &edge_to_child, const size_t depth_level ) = 0;
                        };

                        /** Depth-first visit of all children nodes of a given root (itself excluded from the visit), invoking a user-provided function for each node/edge. \sa visitBreadthFirst */
                        void visitDepthFirst( const TNodeID root, Visitor & user_visitor, const size_t root_depth_level =0 ) const
                        {
                                const size_t next_depth_level = root_depth_level+1;
                                typename TMapNode2ListEdges::const_iterator itChildren = edges_to_children.find(root);
                                if (itChildren==edges_to_children.end()) return; // No children
                                const TListEdges &children = itChildren->second;
                                for (typename TListEdges::const_iterator itEdge=children.begin();itEdge!=children.end();++itEdge)
                                {
                                        user_visitor.OnVisitNode(root,*itEdge,next_depth_level);
                                        visitDepthFirst(itEdge->id,user_visitor, next_depth_level); // Recursive depth-first call.
                                }
                        }

                        /** Breadth-first visit of all children nodes of a given root (itself excluded from the visit), invoking a user-provided function for each node/edge. \sa visitDepthFirst */
                        void visitBreadthFirst( const TNodeID root, Visitor & user_visitor, const size_t root_depth_level =0  ) const
                        {
                                const size_t next_depth_level = root_depth_level+1;
                                typename TMapNode2ListEdges::const_iterator itChildren = edges_to_children.find(root);
                                if (itChildren==edges_to_children.end()) return; // No children
                                const TListEdges &children = itChildren->second;
                                for (typename TListEdges::const_iterator itEdge=children.begin();itEdge!=children.end();++itEdge)
                                        user_visitor.OnVisitNode(root,*itEdge,next_depth_level);
                                for (typename TListEdges::const_iterator itEdge=children.begin();itEdge!=children.end();++itEdge)
                                        visitDepthFirst(itEdge->id,user_visitor,next_depth_level); // Recursive breath-first call.
                        }

                        /** Return a text representation of the tree spanned in a depth-first view, as in this example:
                          *  \code
                          *    0
                          *     -> 1
                          *     -> 2
                          *         -> 4
                          *         -> 5
                          *     -> 3
                          *  \endcode
                          */
                        std::string getAsTextDescription() const
                        {
                                std::ostringstream s;
                                struct CMyVisitor : public mrpt::graphs::CDirectedTree<TYPE_EDGES>::Visitor
                                {
                                        std::ostringstream  &m_s;
                                        CMyVisitor(std::ostringstream &s) : m_s(s) { }
                                        virtual void OnVisitNode( const TNodeID parent, const typename mrpt::graphs::CDirectedTree<TYPE_EDGES>::Visitor::tree_t::TEdgeInfo &edge_to_child, const size_t depth_level ) MRPT_OVERRIDE {
                                                m_s << std::string(depth_level*5, ' ') << (edge_to_child.reverse ? "<-" : "->" ) //;
                                                        << edge_to_child.id << std::endl;
                                        }
                                };
                                CMyVisitor myVisitor(s);
                                s <<  root << std::endl;
                                visitDepthFirst( root, myVisitor );
                                return s.str();
                        }

                };

                /** @} */
        } // End of namespace
} // End of namespace
#endif