1 | // -*- c++ -*- // |
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2 | #ifndef HUGO_KRUSKAL_H |
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3 | #define HUGO_KRUSKAL_H |
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4 | |
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5 | #include "unionfind.h" |
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6 | #include <algorithm> |
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7 | |
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8 | namespace hugo { |
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9 | |
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10 | |
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11 | template <typename Graph, typename EdgeCostMap, typename EdgeBoolMap> |
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12 | class MinCostTreeKruskal |
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13 | { |
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14 | |
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15 | typedef typename Graph::EdgeIt EdgeIt; |
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16 | typedef typename Graph::Edge Edge; |
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17 | |
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18 | public: |
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19 | typedef typename EdgeCostMap::ValueType EdgeCost; |
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20 | typedef std::pair<Edge, EdgeCost> EdgeCostPair; |
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21 | typedef std::vector<EdgeCostPair> EdgeCostVector; |
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22 | |
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23 | private: |
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24 | Graph const &G; |
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25 | EdgeCostMap const &costmap; |
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26 | EdgeBoolMap& treemap; |
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27 | |
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28 | //template <typename EdgeCostPair> |
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29 | class comparePair { |
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30 | public: |
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31 | bool operator()(EdgeCostPair const& a, EdgeCostPair const& b) { |
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32 | return a.second < b.second; |
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33 | } |
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34 | }; |
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35 | |
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36 | public: |
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37 | |
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38 | |
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39 | MinCostTreeKruskal(Graph const& _G, EdgeCostMap const& _costmap, |
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40 | EdgeBoolMap& _treemap) : G(_G), costmap(_costmap), |
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41 | treemap(_treemap) {} |
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42 | |
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43 | |
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44 | EdgeCost run() |
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45 | { |
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46 | EdgeCostVector rank; |
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47 | for (EdgeIt e=G.template first<EdgeIt>(); G.valid(e); G.next(e)) { |
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48 | rank.push_back(make_pair(e, costmap.get(e))); |
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49 | } |
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50 | |
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51 | std::sort(rank.begin(), rank.end(), comparePair()); |
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52 | |
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53 | return run(rank); |
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54 | |
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55 | } |
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56 | |
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57 | EdgeCost run(EdgeCostVector const &rank) |
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58 | { |
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59 | typedef typename Graph::NodeMap<int> NodeIntMap; |
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60 | typedef typename Graph::Node Node; |
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61 | NodeIntMap comp_map(G, -1); |
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62 | UnionFind<Node,NodeIntMap> uf(comp_map); |
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63 | |
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64 | EdgeCost tot_cost = 0; |
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65 | for (typename EdgeCostVector::const_iterator p = rank.begin(); |
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66 | p!=rank.end(); ++p ) { |
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67 | if ( uf.joinComponents(G.head(p->first), G.tail(p->first)) ) { |
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68 | treemap.set(p->first, true); |
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69 | tot_cost += p->second; |
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70 | } |
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71 | else { |
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72 | treemap.set(p->first, false); |
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73 | } |
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74 | } |
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75 | return tot_cost; |
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76 | |
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77 | } |
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78 | |
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79 | }; |
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80 | |
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81 | |
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82 | } //namespace hugo |
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83 | |
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84 | #endif //HUGO_KRUSKAL_H |
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