COIN-OR::LEMON - Graph Library

source: lemon-0.x/demo/kruskal_demo.cc @ 1610:893dacc1866c

Last change on this file since 1610:893dacc1866c was 1584:cf4bc8d477f4, checked in by zsuzska, 14 years ago

corrections

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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 <iostream>
25#include <vector>
26
27#include <lemon/maps.h>
28#include <lemon/kruskal.h>
29#include <lemon/list_graph.h>
30
31
32using namespace std;
33using namespace lemon;
34
35
36int main() {
37
38  typedef ListGraph::Node Node;
39  typedef ListGraph::Edge Edge;
40  typedef ListGraph::NodeIt NodeIt;
41  typedef ListGraph::EdgeIt EdgeIt;
42
43  ListGraph g;
44  //Make an example graph g.
45  Node s=g.addNode();
46  Node v1=g.addNode();
47  Node v2=g.addNode();
48  Node v3=g.addNode();
49  Node v4=g.addNode();
50  Node t=g.addNode();
51 
52  Edge e1 = g.addEdge(s, v1);
53  Edge e2 = g.addEdge(s, v2);
54  Edge e3 = g.addEdge(v1, v2);
55  Edge e4 = g.addEdge(v2, v1);
56  Edge e5 = g.addEdge(v1, v3);
57  Edge e6 = g.addEdge(v3, v2);
58  Edge e7 = g.addEdge(v2, v4);
59  Edge e8 = g.addEdge(v4, v3);
60  Edge e9 = g.addEdge(v3, t);
61  Edge e10 = g.addEdge(v4, t);
62
63  //Make the input for the kruskal.
64  typedef ListGraph::EdgeMap<int> ECostMap;
65  ECostMap edge_cost_map(g);
66
67  // Fill the edge_cost_map.
68  edge_cost_map.set(e1, -10);
69  edge_cost_map.set(e2, -9);
70  edge_cost_map.set(e3, -8);
71  edge_cost_map.set(e4, -7);
72  edge_cost_map.set(e5, -6);
73  edge_cost_map.set(e6, -5);
74  edge_cost_map.set(e7, -4);
75  edge_cost_map.set(e8, -3);
76  edge_cost_map.set(e9, -2);
77  edge_cost_map.set(e10, -1);
78
79  // Make the map or the vector, which will contain the edges of the minimum
80  // spanning tree.
81
82  typedef ListGraph::EdgeMap<bool> EBoolMap;
83  EBoolMap tree_map(g);
84
85  vector<Edge> tree_edge_vec;
86
87
88  //Kruskal Algorithm. 
89
90  //Input: a graph (g); a costmap of the graph (edge_cost_map); a
91  //boolmap (tree_map) or a vector (tree_edge_vec) to store the edges
92  //of the output tree;
93
94  //Output: it gives back the value of the minimum spanning tree, and
95  //set true for the edges of the tree in the edgemap tree_map or
96  //store the edges of the tree in the vector tree_edge_vec;
97
98
99  // Kruskal with boolmap;
100  std::cout << "The weight of the minimum spanning tree is " <<
101    kruskal(g, edge_cost_map, tree_map)<<std::endl;
102
103  int k=0;
104  std::cout << "The edges of the tree:" ;
105  for(EdgeIt i(g); i!=INVALID; ++i){
106
107    if (tree_map[i]) {
108      std::cout << g.id(i) <<";";
109      ++k;
110    }
111  }
112  std::cout << std::endl;
113  std::cout << "The size of the tree is: "<< k << std::endl;
114
115
116  // Kruskal with vector;
117  std::cout << "The weight of the minimum spanning tree again is " <<
118    kruskal(g, edge_cost_map, std::back_inserter(tree_edge_vec)) <<std::endl;
119
120
121
122  std::cout << "The edges of the tree again: " ;
123  for(int i=tree_edge_vec.size()-1; i>=0;  i--)
124    std::cout << g.id(tree_edge_vec[i]) << ";" ;
125  std::cout << std::endl;
126  std::cout << "The size of the tree again is: "<< tree_edge_vec.size()<< std::endl;
127
128 
129  return 0;
130}
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