COIN-OR::LEMON - Graph Library

source: lemon-0.x/demo/kruskal_demo.cc @ 1641:77f6ab7ad66f

Last change on this file since 1641:77f6ab7ad66f was 1641:77f6ab7ad66f, checked in by Alpar Juttner, 14 years ago

Demos' documentations include the source.

File size: 3.5 KB
Line 
1/* -*- C++ -*-
2 * demo/kruskal_demo.cc - Part of LEMON, a generic C++ optimization library
3 *
4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Research Group on Combinatorial Optimization, EGRES).
6 *
7 * Permission to use, modify and distribute this software is granted
8 * provided that this copyright notice appears in all copies. For
9 * precise terms see the accompanying LICENSE file.
10 *
11 * This software is provided "AS IS" with no warranty of any kind,
12 * express or implied, and with no claim as to its suitability for any
13 * purpose.
14 *
15 */
16
17///\ingroup demos
18///\file
19///\brief Minimum weight spanning tree by Kruskal algorithm (demo).
20///
21/// This demo program shows how to find a minimum weight spanning tree
22/// in a graph by using the Kruskal algorithm.
23///
24/// \include kruskal_demo.cc
25
26#include <iostream>
27#include <vector>
28
29#include <lemon/maps.h>
30#include <lemon/kruskal.h>
31#include <lemon/list_graph.h>
32
33
34using namespace std;
35using namespace lemon;
36
37
38int main() {
39
40  typedef ListGraph::Node Node;
41  typedef ListGraph::Edge Edge;
42  typedef ListGraph::NodeIt NodeIt;
43  typedef ListGraph::EdgeIt EdgeIt;
44
45  ListGraph g;
46  //Make an example graph g.
47  Node s=g.addNode();
48  Node v1=g.addNode();
49  Node v2=g.addNode();
50  Node v3=g.addNode();
51  Node v4=g.addNode();
52  Node t=g.addNode();
53 
54  Edge e1 = g.addEdge(s, v1);
55  Edge e2 = g.addEdge(s, v2);
56  Edge e3 = g.addEdge(v1, v2);
57  Edge e4 = g.addEdge(v2, v1);
58  Edge e5 = g.addEdge(v1, v3);
59  Edge e6 = g.addEdge(v3, v2);
60  Edge e7 = g.addEdge(v2, v4);
61  Edge e8 = g.addEdge(v4, v3);
62  Edge e9 = g.addEdge(v3, t);
63  Edge e10 = g.addEdge(v4, t);
64
65  //Make the input for the kruskal.
66  typedef ListGraph::EdgeMap<int> ECostMap;
67  ECostMap edge_cost_map(g);
68
69  // Fill the edge_cost_map.
70  edge_cost_map.set(e1, -10);
71  edge_cost_map.set(e2, -9);
72  edge_cost_map.set(e3, -8);
73  edge_cost_map.set(e4, -7);
74  edge_cost_map.set(e5, -6);
75  edge_cost_map.set(e6, -5);
76  edge_cost_map.set(e7, -4);
77  edge_cost_map.set(e8, -3);
78  edge_cost_map.set(e9, -2);
79  edge_cost_map.set(e10, -1);
80
81  // Make the map or the vector, which will contain the edges of the minimum
82  // spanning tree.
83
84  typedef ListGraph::EdgeMap<bool> EBoolMap;
85  EBoolMap tree_map(g);
86
87  vector<Edge> tree_edge_vec;
88
89
90  //Kruskal Algorithm. 
91
92  //Input: a graph (g); a costmap of the graph (edge_cost_map); a
93  //boolmap (tree_map) or a vector (tree_edge_vec) to store the edges
94  //of the output tree;
95
96  //Output: it gives back the value of the minimum spanning tree, and
97  //set true for the edges of the tree in the edgemap tree_map or
98  //store the edges of the tree in the vector tree_edge_vec;
99
100
101  // Kruskal with boolmap;
102  std::cout << "The weight of the minimum spanning tree is " <<
103    kruskal(g, edge_cost_map, tree_map)<<std::endl;
104
105  int k=0;
106  std::cout << "The edges of the tree:" ;
107  for(EdgeIt i(g); i!=INVALID; ++i){
108
109    if (tree_map[i]) {
110      std::cout << g.id(i) <<";";
111      ++k;
112    }
113  }
114  std::cout << std::endl;
115  std::cout << "The size of the tree is: "<< k << std::endl;
116
117
118  // Kruskal with vector;
119  std::cout << "The weight of the minimum spanning tree again is " <<
120    kruskal(g, edge_cost_map, std::back_inserter(tree_edge_vec)) <<std::endl;
121
122
123
124  std::cout << "The edges of the tree again: " ;
125  for(int i=tree_edge_vec.size()-1; i>=0;  i--)
126    std::cout << g.id(tree_edge_vec[i]) << ";" ;
127  std::cout << std::endl;
128  std::cout << "The size of the tree again is: "<< tree_edge_vec.size()
129            << std::endl;
130
131 
132  return 0;
133}
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