COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/demo/sub_graph_wrapper_demo.cc @ 869:c19cf2007a7a

Last change on this file since 869:c19cf2007a7a was 869:c19cf2007a7a, checked in by marci, 16 years ago

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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 disjoint shortest paths
6// between s and t.
7
8#include <iostream>
9#include <fstream>
10
11#include <hugo/smart_graph.h>
12#include <hugo/dijkstra.h>
13#include <hugo/maps.h>
14#include <hugo/graph_wrapper.h>
15#include <hugo/dimacs.h>
16#include <hugo/preflow.h>
17#include <tight_edge_filter_map.h>
18
19using namespace hugo;
20
21using std::cout;
22using std::endl;
23
24int 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 tail--length->head): " << endl;
41  for(EdgeIt e(g); e!=INVALID; ++e)
42    cout << " " << g.id(g.tail(e)) << "--"
43         << length[e] << "->" << g.id(g.head(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  SubGW gw(g, const_true_map, tight_edge_filter);
62
63  ConstMap<Edge, int> const_1_map(1);
64  Graph::EdgeMap<int> flow(g, 0);
65  // Max flow between s and t in the graph of tight edges.
66  Preflow<SubGW, int, ConstMap<Edge, int>, Graph::EdgeMap<int> >
67    preflow(gw, s, t, const_1_map, flow);
68  preflow.run();
69
70  cout << "edges of the maximum number of edge-disjoint shortest s-t paths: "
71       << endl;
72  for(EdgeIt e(g); e!=INVALID; ++e)
73    if (flow[e])
74      cout << " " << g.id(g.tail(e)) << "--"
75           << length[e] << "->" << g.id(g.head(e)) << endl;
76
77  return 0;
78}
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