[1199] | 1 | #ifndef LEMON_GREEDY_TSP_H |
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| 2 | #define LEMON_GREEDY_TSP_H |
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| 3 | |
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| 4 | #include <lemon/path.h> |
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| 5 | #include <lemon/full_graph.h> |
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| 6 | #include <lemon/unionfind.h> |
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| 7 | #include <algorithm> |
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| 8 | |
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| 9 | namespace lemon { |
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| 10 | |
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| 11 | namespace greedy_tsp_helper { |
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| 12 | |
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| 13 | template <typename CostMap> |
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| 14 | class KeyComp { |
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| 15 | typedef typename CostMap::Key Key; |
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| 16 | const CostMap &cost; |
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| 17 | |
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| 18 | public: |
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| 19 | KeyComp(const CostMap &_cost) : cost(_cost) {} |
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| 20 | |
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| 21 | bool operator() (const Key &a, const Key &b) const { |
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| 22 | return cost[a] < cost[b]; |
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| 23 | } |
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| 24 | }; |
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| 25 | |
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| 26 | |
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| 27 | template <class L> |
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| 28 | L vectorConvert(const std::vector<FullGraph::Node> &_path) { |
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| 29 | return L(_path.begin(), _path.end()); |
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| 30 | } |
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| 31 | |
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| 32 | template <> |
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| 33 | std::vector<FullGraph::Node> vectorConvert(const std::vector<FullGraph::Node> &_path) { |
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| 34 | return _path; |
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| 35 | } |
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| 36 | |
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| 37 | } |
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| 38 | |
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| 39 | |
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| 40 | template <typename CM> |
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| 41 | class GreedyTsp { |
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| 42 | private: |
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| 43 | GRAPH_TYPEDEFS(FullGraph); |
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| 44 | |
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| 45 | public: |
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| 46 | typedef CM CostMap; |
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| 47 | typedef typename CM::Value Cost; |
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| 48 | |
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| 49 | GreedyTsp(const FullGraph &gr, const CostMap &cost) : _gr(gr), _cost(cost) {} |
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| 50 | |
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| 51 | Cost run() { |
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| 52 | typedef UnionFind<FullGraph::NodeMap<int> > Union; |
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| 53 | _nodes.clear(); |
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| 54 | |
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| 55 | std::vector<int> path; |
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| 56 | path.resize(_gr.nodeNum()*2, -1); |
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| 57 | |
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| 58 | std::vector<typename CostMap::Key> sorted_edges; |
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| 59 | sorted_edges.reserve(_gr.edgeNum()); |
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| 60 | for (EdgeIt n(_gr); n != INVALID; ++n) |
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| 61 | sorted_edges.push_back(n); |
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| 62 | |
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| 63 | std::sort(sorted_edges.begin(), sorted_edges.end(), greedy_tsp_helper::KeyComp<CostMap>(_cost)); |
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| 64 | |
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| 65 | FullGraph::NodeMap<int> nodemap(_gr); |
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| 66 | Union unionfind(nodemap); |
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| 67 | |
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| 68 | for (NodeIt n(_gr); n != INVALID; ++n) |
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| 69 | unionfind.insert(n); |
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| 70 | |
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| 71 | FullGraph::NodeMap<int> degree(_gr, 0); |
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| 72 | |
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| 73 | int nodesNum = 0, i = 0; |
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| 74 | |
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| 75 | while ( nodesNum != _gr.nodeNum()-1 ) { |
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| 76 | const Edge &e = sorted_edges[i]; |
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| 77 | |
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| 78 | const Node u = _gr.u(e), |
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| 79 | v = _gr.v(e); |
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| 80 | |
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| 81 | if (degree[u]<=1 && degree[v]<=1) { |
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| 82 | if (unionfind.join(u, v)) { |
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| 83 | ++degree[u]; |
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| 84 | ++degree[v]; |
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| 85 | ++nodesNum; |
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| 86 | |
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| 87 | const int uid = _gr.id(u), |
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| 88 | vid = _gr.id(v); |
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| 89 | |
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| 90 | |
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| 91 | path[uid*2 + (path[uid*2]==-1 ? 0 : 1)] = vid; |
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| 92 | path[vid*2 + (path[vid*2]==-1 ? 0 : 1)] = uid; |
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| 93 | } |
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| 94 | } |
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| 95 | |
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| 96 | ++i; |
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| 97 | } |
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| 98 | |
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| 99 | |
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| 100 | for (int i=0, n=-1; i<_gr.nodeNum()*2; ++i) { |
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| 101 | if (path[i] == -1) { |
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| 102 | if (n==-1) { |
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| 103 | n = i; |
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| 104 | } else { |
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| 105 | path[n] = i/2; |
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| 106 | path[i] = n/2; |
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| 107 | break; |
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| 108 | } |
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| 109 | } |
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| 110 | } |
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| 111 | |
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| 112 | |
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| 113 | for (int i=0, j=0, last=-1; i!=_gr.nodeNum(); ++i) { |
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| 114 | _nodes.push_back(_gr.nodeFromId(j)); |
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| 115 | |
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| 116 | if (path[2*j] != last) { |
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| 117 | last = j; |
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| 118 | j = path[2*j]; |
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| 119 | } else { |
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| 120 | last = j; |
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| 121 | j = path[2*j+1]; |
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| 122 | } |
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| 123 | } |
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| 124 | |
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| 125 | _sum = _cost[_gr.edge(_nodes.back(), _nodes.front())]; |
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| 126 | for (unsigned int i=0; i<_nodes.size()-1; ++i) |
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| 127 | _sum += _cost[_gr.edge(_nodes[i], _nodes[i+1])]; |
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| 128 | |
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| 129 | return _sum; |
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| 130 | } |
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| 131 | |
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| 132 | |
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| 133 | |
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| 134 | template <typename L> |
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| 135 | void tourNodes(L &container) { |
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| 136 | container(greedy_tsp_helper::vectorConvert<L>(_nodes)); |
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| 137 | } |
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| 138 | |
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| 139 | template <template <typename> class L> |
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| 140 | L<Node> tourNodes() { |
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| 141 | return greedy_tsp_helper::vectorConvert<L<Node> >(_nodes); |
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| 142 | } |
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| 143 | |
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| 144 | const std::vector<Node>& tourNodes() { |
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| 145 | return _nodes; |
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| 146 | } |
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| 147 | |
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| 148 | Path<FullGraph> tour() { |
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| 149 | Path<FullGraph> p; |
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| 150 | if (_nodes.size()<2) |
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| 151 | return p; |
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| 152 | |
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| 153 | for (unsigned int i=0; i<_nodes.size()-1; ++i) { |
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| 154 | p.addBack(_gr.arc(_nodes[i], _nodes[i+1])); |
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| 155 | } |
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| 156 | |
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| 157 | p.addBack(_gr.arc(_nodes.back(), _nodes.front())); |
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| 158 | |
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| 159 | return p; |
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| 160 | } |
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| 161 | |
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| 162 | Cost tourCost() { |
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| 163 | return _sum; |
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| 164 | } |
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| 165 | |
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| 166 | |
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| 167 | private: |
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| 168 | const FullGraph &_gr; |
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| 169 | const CostMap &_cost; |
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| 170 | Cost _sum; |
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| 171 | std::vector<Node> _nodes; |
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| 172 | }; |
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| 173 | |
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| 174 | }; // namespace lemon |
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| 175 | |
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| 176 | #endif |
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