// -*- c++ -*-

// Use a DIMACS max flow file as input.

// sub_graph_adaptor_demo < dimacs_max_flow_file

// This program computes a maximum number of edge-disjoint shortest paths

// between s and t.

#include <iostream>

#include <fstream>

#include <lemon/smart_graph.h>

#include <lemon/dijkstra.h>

#include <lemon/maps.h>

#include <lemon/graph_adaptor.h>

#include <lemon/dimacs.h>

#include <lemon/preflow.h>

#include <tight_edge_filter_map.h>

using namespace lemon;

using std::cout;

using std::endl;

int main(int argc, char *argv[]) 

{

  if(argc<2)

  {

      std::cerr << "USAGE: sub_graph_adaptor_demo <input_file.dim>" << std::endl;

      std::cerr << "The file 'input_file.dim' has to contain a max flow instance in DIMACS format (e.g. sub_graph_adaptor_demo.dim is such a file)." << std::endl;

      return 0;

  }

  //input stream to read the graph from

  std::ifstream is(argv[1]);

  typedef SmartGraph Graph;

  typedef Graph::Edge Edge;

  typedef Graph::Node Node;

  typedef Graph::EdgeIt EdgeIt;

  typedef Graph::NodeIt NodeIt;

  typedef Graph::EdgeMap<int> LengthMap;

  Graph g;

  Node s, t;

  LengthMap length(g);

  readDimacs(is, g, length, s, t);

  cout << "edges with lengths (of form id, source--length->target): " << endl;

  for(EdgeIt e(g); e!=INVALID; ++e) 

    cout << " " << g.id(e) << ", " << g.id(g.source(e)) << "--" 

	 << length[e] << "->" << g.id(g.target(e)) << endl;

  cout << "s: " << g.id(s) << " t: " << g.id(t) << endl;

  typedef Dijkstra<Graph, LengthMap> Dijkstra;

  Dijkstra dijkstra(g, length);

  dijkstra.run(s);

  // This map returns true exactly for those edges which are 

  // tight w.r.t the length funcion and the potential 

  // given by the dijkstra algorithm.

  typedef TightEdgeFilterMap<Graph, const Dijkstra::DistMap, LengthMap> 

    TightEdgeFilter;

  TightEdgeFilter tight_edge_filter(g, dijkstra.distMap(), length);

//  ConstMap<Node, bool> const_true_map(true);

  // This graph contains exaclty the tight edges.

// typedef SubGraphAdaptor<Graph, ConstMap<Node, bool>, TightEdgeFilter> SubGW;

  typedef EdgeSubGraphAdaptor<Graph, TightEdgeFilter> SubGW;

  SubGW gw(g, tight_edge_filter);

  ConstMap<Edge, int> const_1_map(1);

  Graph::EdgeMap<int> flow(g, 0);

  // Max flow between s and t in the graph of tight edges.

  Preflow<SubGW, int, ConstMap<Edge, int>, Graph::EdgeMap<int> > 

    preflow(gw, s, t, const_1_map, flow);

  preflow.run();

  cout << "maximum number of edge-disjoint shortest paths: " 

       << preflow.flowValue() << endl;

  cout << "edges of the maximum number of edge-disjoint shortest s-t paths: " 

       << endl;

  for(EdgeIt e(g); e!=INVALID; ++e) 

    if (flow[e])

      cout << " " << g.id(e) << ", "

	   << g.id(g.source(e)) << "--" 

	   << length[e] << "->" << g.id(g.target(e)) << endl;

}