1 | // -*- c++ -*- |
---|
2 | |
---|
3 | // Use a DIMACS max flow file as stdin. |
---|
4 | // sub_graph_wrapper_demo < dimacs_max_flow_file |
---|
5 | // This program computes a maximum number of edge-disjoint shortest paths |
---|
6 | // between s and t. |
---|
7 | |
---|
8 | #include <iostream> |
---|
9 | #include <fstream> |
---|
10 | |
---|
11 | #include <lemon/smart_graph.h> |
---|
12 | #include <lemon/dijkstra.h> |
---|
13 | #include <lemon/maps.h> |
---|
14 | #include <lemon/graph_wrapper.h> |
---|
15 | #include <lemon/dimacs.h> |
---|
16 | #include <lemon/preflow.h> |
---|
17 | #include <tight_edge_filter_map.h> |
---|
18 | |
---|
19 | using namespace lemon; |
---|
20 | |
---|
21 | using std::cout; |
---|
22 | using std::endl; |
---|
23 | |
---|
24 | int main() |
---|
25 | { |
---|
26 | typedef SmartGraph Graph; |
---|
27 | |
---|
28 | typedef Graph::Edge Edge; |
---|
29 | typedef Graph::Node Node; |
---|
30 | typedef Graph::EdgeIt EdgeIt; |
---|
31 | typedef Graph::NodeIt NodeIt; |
---|
32 | typedef Graph::EdgeMap<int> LengthMap; |
---|
33 | |
---|
34 | Graph g; |
---|
35 | Node s, t; |
---|
36 | LengthMap length(g); |
---|
37 | |
---|
38 | readDimacs(std::cin, g, length, s, t); |
---|
39 | |
---|
40 | cout << "edges with lengths (of form id, source--length->target): " << endl; |
---|
41 | for(EdgeIt e(g); e!=INVALID; ++e) |
---|
42 | cout << " " << g.id(e) << ", " << g.id(g.source(e)) << "--" |
---|
43 | << length[e] << "->" << g.id(g.target(e)) << endl; |
---|
44 | |
---|
45 | cout << "s: " << g.id(s) << " t: " << g.id(t) << endl; |
---|
46 | |
---|
47 | typedef Dijkstra<Graph, LengthMap> Dijkstra; |
---|
48 | Dijkstra dijkstra(g, length); |
---|
49 | dijkstra.run(s); |
---|
50 | |
---|
51 | // This map returns true exactly for those edges which are |
---|
52 | // tight w.r.t the length funcion and the potential |
---|
53 | // given by the dijkstra algorithm. |
---|
54 | typedef TightEdgeFilterMap<Graph, const Dijkstra::DistMap, LengthMap> |
---|
55 | TightEdgeFilter; |
---|
56 | TightEdgeFilter tight_edge_filter(g, dijkstra.distMap(), length); |
---|
57 | |
---|
58 | // ConstMap<Node, bool> const_true_map(true); |
---|
59 | // This graph contains exaclty the tight edges. |
---|
60 | // typedef SubGraphWrapper<Graph, ConstMap<Node, bool>, TightEdgeFilter> SubGW; |
---|
61 | typedef EdgeSubGraphWrapper<Graph, TightEdgeFilter> SubGW; |
---|
62 | SubGW gw(g, tight_edge_filter); |
---|
63 | |
---|
64 | ConstMap<Edge, int> const_1_map(1); |
---|
65 | Graph::EdgeMap<int> flow(g, 0); |
---|
66 | // Max flow between s and t in the graph of tight edges. |
---|
67 | Preflow<SubGW, int, ConstMap<Edge, int>, Graph::EdgeMap<int> > |
---|
68 | preflow(gw, s, t, const_1_map, flow); |
---|
69 | preflow.run(); |
---|
70 | |
---|
71 | cout << "maximum number of edge-disjoint shortest path: " |
---|
72 | << preflow.flowValue() << endl; |
---|
73 | cout << "edges of the maximum number of edge-disjoint shortest s-t paths: " |
---|
74 | << endl; |
---|
75 | for(EdgeIt e(g); e!=INVALID; ++e) |
---|
76 | if (flow[e]) |
---|
77 | cout << " " << g.id(e) << ", " |
---|
78 | << g.id(g.source(e)) << "--" |
---|
79 | << length[e] << "->" << g.id(g.target(e)) << endl; |
---|
80 | } |
---|