/* -*- mode: C++; indent-tabs-mode: nil; -*-

  *

  * This file is a part of LEMON, a generic C++ optimization library.

  *

  * Copyright (C) 2003-2009

  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

  * (Egervary Research Group on Combinatorial Optimization, EGRES).

  *

  * Permission to use, modify and distribute this software is granted

  * provided that this copyright notice appears in all copies. For

  * precise terms see the accompanying LICENSE file.

  *

  * This software is provided "AS IS" with no warranty of any kind,

  * express or implied, and with no claim as to its suitability for any

  * purpose.

  *

  */

 #ifndef LEMON_NAUTY_READER_H

 #define LEMON_NAUTY_READER_H

 #include <vector>

 #include <iostream>

 #include <string>

 /// \ingroup nauty_group

 /// \file

 /// \brief Nauty file reader.

 namespace lemon {

   /// \ingroup nauty_group

   ///

   /// \brief Nauty file reader

   ///

   /// The \e geng program is in the \e gtools suite of the nauty

   /// package. This tool can generate all non-isomorphic undirected

   /// graphs of several classes with given node number (e.g.

   /// general, connected, biconnected, triangle-free, 4-cycle-free,

   /// bipartite and graphs with given edge number and degree

   /// constraints). This function reads a \e nauty \e graph6 \e format

   /// line from the given stream and builds it in the given graph.

   ///

   /// The site of nauty package: http://cs.anu.edu.au/~bdm/nauty/

   ///

   /// For example, the number of all non-isomorphic planar graphs

   /// can be computed with the following code.

   ///\code

   /// int num = 0;

   /// SmartGraph graph;

   /// while (readNautyGraph(graph, std::cin)) {

   ///   PlanarityChecking<SmartGraph> pc(graph);

   ///   if (pc.run()) ++num;

   /// }

   /// std::cout << "Number of planar graphs: " << num << std::endl;

   ///\endcode

   ///

   /// The nauty files are quite huge, therefore instead of the direct

   /// file generation pipelining is recommended. For example,

   ///\code

   /// ./geng -c 10 | ./num_of_planar_graphs

   ///\endcode

   template <typename Graph>

   std::istream& readNautyGraph(Graph& graph, std::istream& is = std::cin) {

     graph.clear();

     std::string line;

     if (getline(is, line)) {

       int index = 0;

       int n;

       if (line[index] == '>') {

         index += 10;

       }

       char c = line[index++]; c -= 63;

       if (c != 63) {

         n = int(c);

       } else {

         c = line[index++]; c -= 63;

         n = (int(c) << 12);

         c = line[index++]; c -= 63;

         n |= (int(c) << 6);

         c = line[index++]; c -= 63;

         n |= int(c);

       }

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

       for (int i = 0; i < n; ++i) {

         nodes.push_back(graph.addNode());

       }

       int bit = -1;

       for (int j = 0; j < n; ++j) {

         for (int i = 0; i < j; ++i) {

           if (bit == -1) {

             c = line[index++]; c -= 63;

             bit = 5;

           }

           bool b = (c & (1 << (bit--))) != 0;

           if (b) {

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

           }

         }

       }

     }

     return is;

   }

 }

 #endif