source: lemon-0.x/demo/kruskal_demo.cc @ 1578:1d3a1bcbc874

/* -*- C++ -*-
 * demo/kruskal_demo.cc - Part of LEMON, a generic C++ optimization library
 *
 * Copyright (C) 2005 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.
 *
 */

///\ingroup demos
///\file
///\brief Minimum weight spanning tree by Kruskal algorithm (demo).
///
///This demo program shows how to find a minimum weight spannin tree
///of a graph by using the Kruskal algorithm. 

#include <iostream>
#include <vector>

#include <lemon/maps.h>
#include <lemon/kruskal.h>
#include <lemon/list_graph.h>


using namespace std;
using namespace lemon;


int main() {

  typedef ListGraph::Node Node;
  typedef ListGraph::Edge Edge;
  typedef ListGraph::NodeIt NodeIt;
  typedef ListGraph::EdgeIt EdgeIt;

  ListGraph g;
  //Make an example graph g.
  Node s=g.addNode();
  Node v1=g.addNode();
  Node v2=g.addNode();
  Node v3=g.addNode();
  Node v4=g.addNode();
  Node t=g.addNode();
  
  Edge e1 = g.addEdge(s, v1);
  Edge e2 = g.addEdge(s, v2);
  Edge e3 = g.addEdge(v1, v2);
  Edge e4 = g.addEdge(v2, v1);
  Edge e5 = g.addEdge(v1, v3);
  Edge e6 = g.addEdge(v3, v2);
  Edge e7 = g.addEdge(v2, v4);
  Edge e8 = g.addEdge(v4, v3);
  Edge e9 = g.addEdge(v3, t);
  Edge e10 = g.addEdge(v4, t);

  //Make the input and output for the kruskal.
  typedef ListGraph::EdgeMap<int> ECostMap;
  typedef ListGraph::EdgeMap<bool> EBoolMap;

  ECostMap edge_cost_map(g, 2);
  EBoolMap tree_map(g);

  // Kruskal.
  std::cout << "The weight of the minimum spanning tree by using Kruskal algorithm is " 
            << kruskal(g, ConstMap<ListGraph::Edge,int>(2), tree_map)<<std::endl;

  //Make another input (non-uniform costs) for the kruskal.
  ECostMap edge_cost_map_2(g);
  edge_cost_map_2.set(e1, -10);
  edge_cost_map_2.set(e2, -9);
  edge_cost_map_2.set(e3, -8);
  edge_cost_map_2.set(e4, -7);
  edge_cost_map_2.set(e5, -6);
  edge_cost_map_2.set(e6, -5);
  edge_cost_map_2.set(e7, -4);
  edge_cost_map_2.set(e8, -3);
  edge_cost_map_2.set(e9, -2);
  edge_cost_map_2.set(e10, -1);

  vector<Edge> tree_edge_vec;

  //Test with non uniform costs and inserter.
  std::cout << "The weight of the minimum spanning tree with non-uniform costs is " << 
    kruskal(g, edge_cost_map_2, std::back_inserter(tree_edge_vec)) <<std::endl;

  //The vector for the edges of the output tree.
  tree_edge_vec.clear();

  //Test with makeKruskalSequenceOutput and makeKruskalSequenceOutput.

  std::cout << "The weight of the minimum spanning tree again is " << 
   kruskal(g,makeKruskalMapInput(g,edge_cost_map_2),makeKruskalSequenceOutput(std::back_inserter(tree_edge_vec)))<< std::endl;


  return 0;
}