3 * This file is a part of LEMON, a generic C++ optimization library
5 * Copyright (C) 2003-2008
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
20 @defgroup graph_adaptors Adaptor Classes for Graphs
22 \brief This group contains several adaptor classes for graphs
24 The main parts of LEMON are the different graph structures,
25 generic graph algorithms, graph concepts which couple these, and
26 graph adaptors. While the previous notions are more or less clear, the
27 latter one needs further explanation.
28 Graph adaptors are graph classes which serve for considering graph
29 structures in different ways.
31 A short example makes this much
33 Suppose that we have an instance \c g of a directed graph
34 type say ListGraph and an algorithm
35 \code template<typename Graph> int algorithm(const Graph&); \endcode
36 is needed to run on the reversed oriented graph.
37 It may be expensive (in time or in memory usage) to copy
38 \c g with the reversed orientation.
39 In this case, an adaptor class is used, which
40 (according to LEMON graph concepts) works as a graph.
42 the original graph structure and graph operations when methods of the
43 reversed oriented graph are called.
44 This means that the adaptor have minor memory usage,
45 and do not perform sophisticated algorithmic actions.
46 The purpose of it is to give a tool for the cases when
47 a graph have to be used in a specific alteration.
48 If this alteration is obtained by a usual construction
49 like filtering the edge-set or considering a new orientation, then
50 an adaptor is worthwhile to use.
51 To come back to the reversed oriented graph, in this situation
52 \code template<typename Graph> class RevGraphAdaptor; \endcode
53 template class can be used.
54 The code looks as follows
57 RevGraphAdaptor<ListGraph> rga(g);
58 int result=algorithm(rga);
60 After running the algorithm, the original graph \c g
62 This techniques gives rise to an elegant code, and
63 based on stable graph adaptors, complex algorithms can be
66 In flow, circulation and bipartite matching problems, the residual
67 graph is of particular importance. Combining an adaptor implementing
68 this, shortest path algorithms and minimum mean cycle algorithms,
69 a range of weighted and cardinality optimization algorithms can be
72 the interested user is referred to the detailed documentation of
75 The behavior of graph adaptors can be very different. Some of them keep
76 capabilities of the original graph while in other cases this would be
77 meaningless. This means that the concepts that they are models of depend
78 on the graph adaptor, and the wrapped graph(s).
79 If an edge of \c rga is deleted, this is carried out by
80 deleting the corresponding edge of \c g, thus the adaptor modifies the
83 graph, this operation has no sense.
84 Let us stand one more example here to simplify your work.
85 RevGraphAdaptor has constructor
87 RevGraphAdaptor(Graph& _g);
89 This means that in a situation,
90 when a <tt> const ListGraph& </tt> reference to a graph is given,
91 then it have to be instantiated with <tt>Graph=const ListGraph</tt>.
93 int algorithm1(const ListGraph& g) {
94 RevGraphAdaptor<const ListGraph> rga(g);
95 return algorithm2(rga);