/// Dimacs flow file format reader function.

   /// \addtogroup misc

   /// This function reads a flow instance from dimacs flow format.

   /// @{

   /// At the beginning \c g is cleared by \c g.clear().

   /// If the data coming from \c is is a max flow problem instance, then 

   /// Dimacs min cost flow reader function.

   /// \c s and \c t will be respectively the source and target nodes 

   /// and \c capacity will contain the edge capacities.

   /// This function reads a min cost flow instance from dimacs format,

   /// If the data is a shortest path problem instance then \c s will be the 

   /// i.e. from dimacs files having a line starting with \c p \c "min".

   /// source node and \c capacity will contain the edge lengths.

   /// At the beginning \c g is cleared by \c g.clear(). The edge

   ///

   /// capacities are written to \c capacity, \c s and \c t are set to

   ///\author Marton Makai

   /// the source and the target nodes resp. and the cost of the edges

   template<typename Graph, typename CapacityMap>

   /// are written to \c cost.

   void readDimacsMaxFlow(std::istream& is, Graph &g, 

   ///

 			 typename Graph::Node &s, typename Graph::Node &t, CapacityMap& capacity) {

   /// \author Marton Makai

     g.clear();

     int cap;

     char d;

     std::string problem;

     char c;

     int i, j;

     std::string str;

     int n, m; 

     typename Graph::Edge e;

     std::vector<typename Graph::Node> nodes;

     while (is>>c) {

       switch (c) {

       case 'c': //comment

 	getline(is, str);

 	break;

       case 'p': //problem definition

 	is >> problem >> n >> m;

 	getline(is, str);

 	nodes.resize(n+1);

 	for (int k=1; k<=n; ++k) nodes[k]=g.addNode();

 	break;

       case 'n': //node definition

 	if (problem=="sp") { //shortest path problem

 	  is >> i;

 	  getline(is, str);

 	  s=nodes[i];

 	}

 	if (problem=="max") { //max flow problem

 	  is >> i >> d;

 	  getline(is, str);

 	  if (d=='s') s=nodes[i];

 	  if (d=='t') t=nodes[i];

 	}

 	break;

       case 'a':

 	is >> i >> j >> cap;

 	getline(is, str);

 	e=g.addEdge(nodes[i], nodes[j]);

 	capacity.update();

 	capacity.set(e, cap);

 	break;

       }

     }

   }

   /// matching problem

   template<typename Graph>

   void readDimacs(std::istream& is, Graph &g) {

     typename Graph::Node u;

     NullMap<typename Graph::Edge, int> n;

     readDimacs(is, g, n, u, u, n);

   }

   /// sg problem

   template<typename Graph, typename CapacityMap>

   void readDimacs(std::istream& is, Graph &g, CapacityMap& capacity) {

     typename Graph::Node u;

     NullMap<typename Graph::Edge, int> n;

     readDimacs(is, g, capacity, u, u, n);

   }

   /// shortest path problem

   template<typename Graph, typename CapacityMap>

   void readDimacs(std::istream& is, Graph &g, CapacityMap& capacity, 

 		  typename Graph::Node &s) {

     NullMap<typename Graph::Edge, int> n;

     readDimacs(is, g, capacity, s, s, n);

   }

   /// max flow problem

   template<typename Graph, typename CapacityMap>

   void readDimacs(std::istream& is, Graph &g, CapacityMap& capacity, 

 		  typename Graph::Node &s, typename Graph::Node &t) {

     NullMap<typename Graph::Edge, int> n;

     readDimacs(is, g, capacity, s, t, n);

   }

   /// min cost flow problem

 	}

 	} else {

 	if ( problem == "min" ) {

 	  if ( problem == "min" ) {

 	  is >> i >> j >> _cap >> _cost;

 	    is >> i >> j >> _cap >> _cost;

 	  getline(is, str);

 	    getline(is, str);

 	  e=g.addEdge(nodes[i], nodes[j]);

 	    e=g.addEdge(nodes[i], nodes[j]);

 	  capacity.update();

 	    capacity.update();

 	  capacity.set(e, _cap);

 	    capacity.set(e, _cap);

 	  cost.update();

 	    cost.update();

 	  cost.set(e, _cost);

 	    cost.set(e, _cost);

 	  } else {

 	    is >> i >> j;

 	    getline(is, str);

 	    g.addEdge(nodes[i], nodes[j]);

 	  }