COIN-OR::LEMON - Graph Library

source: lemon-0.x/demo/kruskal_demo.cc

Last change on this file was 2553:bfced05fa852, checked in by Alpar Juttner, 12 years ago

Happy New Year to LEMON (+ better update-copyright-header script)

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1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2008
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19///\ingroup demos
20///\file
21///\brief Minimum weight spanning tree by Kruskal algorithm (demo).
22///
23/// This demo program shows how to find a minimum weight spanning tree
24/// in a graph by using the Kruskal algorithm.
25///
26/// \include kruskal_demo.cc
27
28#include <iostream>
29#include <vector>
30
31#include <lemon/maps.h>
32#include <lemon/kruskal.h>
33#include <lemon/list_graph.h>
34
35
36using namespace std;
37using namespace lemon;
38
39
40int main() {
41
42  typedef ListGraph::Node Node;
43  typedef ListGraph::Edge Edge;
44  typedef ListGraph::NodeIt NodeIt;
45  typedef ListGraph::EdgeIt EdgeIt;
46
47  ListGraph g;
48  //Make an example graph g.
49  Node s=g.addNode();
50  Node v1=g.addNode();
51  Node v2=g.addNode();
52  Node v3=g.addNode();
53  Node v4=g.addNode();
54  Node t=g.addNode();
55 
56  Edge e1 = g.addEdge(s, v1);
57  Edge e2 = g.addEdge(s, v2);
58  Edge e3 = g.addEdge(v1, v2);
59  Edge e4 = g.addEdge(v2, v1);
60  Edge e5 = g.addEdge(v1, v3);
61  Edge e6 = g.addEdge(v3, v2);
62  Edge e7 = g.addEdge(v2, v4);
63  Edge e8 = g.addEdge(v4, v3);
64  Edge e9 = g.addEdge(v3, t);
65  Edge e10 = g.addEdge(v4, t);
66
67  //Make the input for the kruskal.
68  typedef ListGraph::EdgeMap<int> ECostMap;
69  ECostMap edge_cost_map(g);
70
71  // Fill the edge_cost_map.
72  edge_cost_map.set(e1, -10);
73  edge_cost_map.set(e2, -9);
74  edge_cost_map.set(e3, -8);
75  edge_cost_map.set(e4, -7);
76  edge_cost_map.set(e5, -6);
77  edge_cost_map.set(e6, -5);
78  edge_cost_map.set(e7, -4);
79  edge_cost_map.set(e8, -3);
80  edge_cost_map.set(e9, -2);
81  edge_cost_map.set(e10, -1);
82
83  // Make the map or the vector, which will contain the edges of the minimum
84  // spanning tree.
85
86  typedef ListGraph::EdgeMap<bool> EBoolMap;
87  EBoolMap tree_map(g);
88
89  vector<Edge> tree_edge_vec;
90
91
92  //Kruskal Algorithm. 
93
94  //Input: a graph (g); a costmap of the graph (edge_cost_map); a
95  //boolmap (tree_map) or a vector (tree_edge_vec) to store the edges
96  //of the output tree;
97
98  //Output: it gives back the value of the minimum spanning tree, and
99  //set true for the edges of the tree in the edgemap tree_map or
100  //store the edges of the tree in the vector tree_edge_vec;
101
102
103  // Kruskal with boolmap;
104  std::cout << "The weight of the minimum spanning tree is " <<
105    kruskal(g, edge_cost_map, tree_map)<<std::endl;
106
107  int k=0;
108  std::cout << "The edges of the tree:" ;
109  for(EdgeIt i(g); i!=INVALID; ++i)
110    if (tree_map[i]) {
111      std::cout << g.id(i) <<";";
112      ++k;
113    }
114
115  std::cout << std::endl;
116  std::cout << "The size of the tree is: "<< k << std::endl;
117
118
119  // Kruskal with vector;
120  std::cout << "The weight of the minimum spanning tree again is " <<
121    kruskal(g, edge_cost_map, std::back_inserter(tree_edge_vec)) <<std::endl;
122
123
124
125  std::cout << "The edges of the tree again: " ;
126  for(int i=tree_edge_vec.size()-1; i>=0;  i--)
127    std::cout << g.id(tree_edge_vec[i]) << ";" ;
128  std::cout << std::endl;
129  std::cout << "The size of the tree again is: "<< tree_edge_vec.size()
130            << std::endl;
131
132 
133  return 0;
134}
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