2 @defgroup graph_adaptors Adaptor Classes for Graphs
4 \brief This group contains several adaptor classes for graphs
6 The main parts of LEMON are the different graph structures,
7 generic graph algorithms, graph concepts which couple these, and
8 graph adaptors. While the previous notions are more or less clear, the
9 latter one needs further explanation.
10 Graph adaptors are graph classes which serve for considering graph
11 structures in different ways.
13 A short example makes this much
15 Suppose that we have an instance \c g of a directed graph
16 type say ListGraph and an algorithm
17 \code template<typename Graph> int algorithm(const Graph&); \endcode
18 is needed to run on the reversed oriented graph.
19 It may be expensive (in time or in memory usage) to copy
20 \c g with the reversed orientation.
21 In this case, an adaptor class is used, which
22 (according to LEMON graph concepts) works as a graph.
24 the original graph structure and graph operations when methods of the
25 reversed oriented graph are called.
26 This means that the adaptor have minor memory usage,
27 and do not perform sophisticated algorithmic actions.
28 The purpose of it is to give a tool for the cases when
29 a graph have to be used in a specific alteration.
30 If this alteration is obtained by a usual construction
31 like filtering the edge-set or considering a new orientation, then
32 an adaptor is worthwhile to use.
33 To come back to the reversed oriented graph, in this situation
34 \code template<typename Graph> class RevGraphAdaptor; \endcode
35 template class can be used.
36 The code looks as follows
39 RevGraphAdaptor<ListGraph> rga(g);
40 int result=algorithm(rga);
42 After running the algorithm, the original graph \c g
44 This techniques gives rise to an elegant code, and
45 based on stable graph adaptors, complex algorithms can be
48 In flow, circulation and bipartite matching problems, the residual
49 graph is of particular importance. Combining an adaptor implementing
50 this, shortest path algorithms and minimum mean cycle algorithms,
51 a range of weighted and cardinality optimization algorithms can be
54 the interested user is referred to the detailed documentation of
57 The behavior of graph adaptors can be very different. Some of them keep
58 capabilities of the original graph while in other cases this would be
59 meaningless. This means that the concepts that they are models of depend
60 on the graph adaptor, and the wrapped graph(s).
61 If an edge of \c rga is deleted, this is carried out by
62 deleting the corresponding edge of \c g, thus the adaptor modifies the
65 graph, this operation has no sense.
66 Let us stand one more example here to simplify your work.
67 RevGraphAdaptor has constructor
69 RevGraphAdaptor(Graph& _g);
71 This means that in a situation,
72 when a <tt> const ListGraph& </tt> reference to a graph is given,
73 then it have to be instantiated with <tt>Graph=const ListGraph</tt>.
75 int algorithm1(const ListGraph& g) {
76 RevGraphAdaptor<const ListGraph> rga(g);
77 return algorithm2(rga);