1 | /* -*- C++ -*- |
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2 | * demo/coloring.cc - Part of LEMON, a generic C++ optimization library |
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3 | * |
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4 | * Copyright (C) 2006 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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5 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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6 | * |
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7 | * Permission to use, modify and distribute this software is granted |
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8 | * provided that this copyright notice appears in all copies. For |
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9 | * precise terms see the accompanying LICENSE file. |
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10 | * |
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11 | * This software is provided "AS IS" with no warranty of any kind, |
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12 | * express or implied, and with no claim as to its suitability for any |
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13 | * purpose. |
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14 | * |
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15 | */ |
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16 | |
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17 | ///\ingroup demos |
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18 | ///\file |
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19 | ///\brief Coloring of a graph. |
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20 | /// |
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21 | /// This example shows how can we color the nodes of a plan graph efficiently |
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22 | /// with six colors. |
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23 | /// |
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24 | /// \include coloring.cc |
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25 | |
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26 | #include <vector> |
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27 | |
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28 | #include <iostream> |
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29 | |
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30 | #include <lemon/smart_graph.h> |
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31 | #include <lemon/linear_heap.h> |
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32 | #include <lemon/graph_reader.h> |
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33 | #include <lemon/graph_to_eps.h> |
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34 | |
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35 | #include <fstream> |
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36 | |
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37 | |
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38 | using namespace std; |
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39 | using namespace lemon; |
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40 | |
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41 | int main() { |
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42 | |
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43 | typedef SmartUGraph Graph; |
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44 | typedef Graph::Node Node; |
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45 | typedef Graph::NodeIt NodeIt; |
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46 | typedef Graph::UEdge UEdge; |
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47 | typedef Graph::IncEdgeIt IncEdgeIt; |
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48 | |
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49 | std::cout << "Six coloring of a plan graph" << std::endl; |
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50 | std::cout << "Input file: coloring.lgf" << std::endl; |
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51 | std::cout << "Output file: coloring.eps" << std::endl; |
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52 | |
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53 | Graph graph; |
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54 | |
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55 | UGraphReader<Graph> reader("coloring.lgf", graph); |
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56 | Graph::NodeMap<xy<double> > coords(graph); |
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57 | reader.readNodeMap("coords", coords); |
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58 | |
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59 | reader.run(); |
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60 | |
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61 | Graph::NodeMap<int> color(graph, -2); |
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62 | |
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63 | Graph::NodeMap<int> heapMap(graph, -1); |
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64 | LinearHeap<Node, Graph::NodeMap<int> > heap(heapMap); |
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65 | |
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66 | for (NodeIt it(graph); it != INVALID; ++it) { |
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67 | heap.push(it, countOutEdges(graph, it)); |
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68 | } |
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69 | |
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70 | vector<Node> order; |
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71 | |
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72 | while (!heap.empty()) { |
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73 | Node node = heap.top(); |
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74 | heap.pop(); |
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75 | color[node] = -1; |
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76 | order.push_back(node); |
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77 | for (IncEdgeIt it(graph, node); it != INVALID; ++it) { |
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78 | Node target = graph.runningNode(it); |
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79 | if (color[target] == -2) { |
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80 | heap.decrease(target, heap[target] - 1); |
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81 | } |
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82 | } |
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83 | } |
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84 | |
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85 | for (int i = order.size() - 1; i >= 0; --i) { |
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86 | set<int> forbidden; |
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87 | for (IncEdgeIt it(graph, order[i]); it != INVALID; ++it) { |
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88 | Node target = graph.runningNode(it); |
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89 | if (color[target] != -1) { |
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90 | forbidden.insert(color[target]); |
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91 | } |
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92 | } |
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93 | int current = 0; |
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94 | while (forbidden.find(current) != forbidden.end()) ++current; |
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95 | color[order[i]] = current; |
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96 | } |
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97 | |
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98 | ColorSet colorSet; |
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99 | |
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100 | graphToEps(graph, "coloring.eps"). |
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101 | title("Six Colored Plan Graph").copyright("(C) 2006 LEMON Project"). |
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102 | coords(coords).nodeColors(composeMap(colorSet, color)). |
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103 | nodeScale(5.0).scaleToA4().run(); |
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104 | |
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105 | return 0; |
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106 | } |
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