1 | // -*- C++ -*- |
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2 | /* |
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3 | *template <Graph, T, Heap=FibHeap, LengthMap=Graph::EdgeMap<T> > |
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4 | * |
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5 | *Constructor: |
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6 | * |
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7 | *Prim(Graph G, LengthMap weight) |
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8 | * |
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9 | * |
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10 | *Methods: |
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11 | * |
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12 | *void run() : Runs the Prim-algorithm from a random node |
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13 | * |
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14 | *void run(Node r) : Runs the Prim-algorithm from node s |
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15 | * |
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16 | *T weight() : After run(r) was run, it returns the minimum |
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17 | * weight of a spanning tree of the component of the root. |
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18 | * |
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19 | *Edge tree(Node v) : After run(r) was run, it returns the |
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20 | * first edge in the path from v to the root. Returns |
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21 | * INVALID if v=r or v is not reachable from the root. |
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22 | * |
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23 | *bool conn() : After run(r) was run, it is true iff G is connected |
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24 | * |
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25 | *bool reached(Node v) : After run(r) was run, it is true |
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26 | * iff v is in the same component as the root |
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27 | * |
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28 | *Node root() : returns the root |
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29 | * |
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30 | */ |
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31 | |
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32 | #ifndef HUGO_PRIM_H |
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33 | #define HUGO_PRIM_H |
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34 | |
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35 | #include <fib_heap.h> |
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36 | #include <invalid.h> |
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37 | |
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38 | namespace hugo { |
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39 | |
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40 | template <typename Graph, typename T, |
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41 | typename Heap=FibHeap<typename Graph::Node, T, |
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42 | typename Graph::NodeMap<int> >, |
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43 | typename LengthMap=typename Graph::EdgeMap<T> > |
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44 | class Prim{ |
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45 | typedef typename Graph::Node Node; |
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46 | typedef typename Graph::NodeIt NodeIt; |
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47 | typedef typename Graph::Edge Edge; |
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48 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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49 | typedef typename Graph::InEdgeIt InEdgeIt; |
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50 | |
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51 | const Graph& G; |
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52 | const LengthMap& edge_weight; |
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53 | typename Graph::NodeMap<Edge> tree_edge; |
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54 | typename Graph::NodeMap<T> min_weight; |
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55 | typename Graph::NodeMap<bool> reach; |
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56 | |
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57 | public : |
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58 | |
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59 | Prim(Graph& _G, LengthMap& _edge_weight) : |
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60 | G(_G), edge_weight(_edge_weight), |
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61 | tree_edge(_G,INVALID), min_weight(_G), reach(_G, false) { } |
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62 | |
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63 | |
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64 | void run() { |
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65 | NodeIt _r; |
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66 | G.first(_r); |
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67 | run(_r); |
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68 | } |
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69 | |
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70 | |
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71 | void run(Node r) { |
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72 | |
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73 | NodeIt u; |
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74 | for ( G.first(u) ; G.valid(u) ; G.next(u) ) { |
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75 | tree_edge.set(u,INVALID); |
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76 | min_weight.set(u,0); |
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77 | reach.set(u,false); |
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78 | } |
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79 | |
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80 | |
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81 | typename Graph::NodeMap<bool> scanned(G, false); |
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82 | typename Graph::NodeMap<int> heap_map(G,-1); |
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83 | |
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84 | Heap heap(heap_map); |
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85 | |
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86 | heap.push(r,0); |
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87 | reach.set(r, true); |
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88 | |
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89 | while ( !heap.empty() ) { |
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90 | |
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91 | Node v=heap.top(); |
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92 | min_weight.set(v, heap.get(v)); |
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93 | heap.pop(); |
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94 | scanned.set(v,true); |
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95 | |
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96 | OutEdgeIt e; |
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97 | for( G.first(e,v); G.valid(e); G.next(e)) { |
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98 | Node w=G.head(e); |
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99 | |
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100 | if ( !scanned[w] ) { |
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101 | if ( !reach[w] ) { |
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102 | reach.set(w,true); |
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103 | heap.push(w, edge_weight[e]); |
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104 | tree_edge.set(w,e); |
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105 | } else if ( edge_weight[e] < heap.get(w) ) { |
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106 | tree_edge.set(w,e); |
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107 | heap.decrease(w, edge_weight[e]); |
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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 | InEdgeIt f; |
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113 | for( G.first(f,v); G.valid(f); G.next(f)) { |
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114 | Node w=G.tail(f); |
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115 | |
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116 | if ( !scanned[w] ) { |
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117 | if ( !reach[w] ) { |
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118 | reach.set(w,true); |
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119 | heap.push(w, edge_weight[f]); |
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120 | tree_edge.set(w,f); |
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121 | } else if ( edge_weight[f] < heap.get(w) ) { |
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122 | tree_edge.set(w,f); |
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123 | heap.decrease(w, edge_weight[f]); |
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124 | } |
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125 | } |
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126 | } |
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127 | } |
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128 | } |
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129 | |
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130 | |
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131 | T weight() { |
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132 | T w=0; |
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133 | NodeIt u; |
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134 | for ( G.first(u) ; G.valid(u) ; G.next(u) ) w+=min_weight[u]; |
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135 | return w; |
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136 | } |
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137 | |
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138 | |
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139 | Edge tree(Node v) { |
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140 | return tree_edge[v]; |
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141 | } |
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142 | |
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143 | |
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144 | bool conn() { |
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145 | bool c=true; |
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146 | NodeIt u; |
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147 | for ( G.first(u) ; G.valid(u) ; G.next(u) ) |
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148 | if ( !reached[u] ) { |
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149 | c=false; |
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150 | break; |
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151 | } |
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152 | return c; |
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153 | } |
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154 | |
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155 | |
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156 | bool reached(Node v) { |
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157 | return reached[v]; |
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158 | } |
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159 | |
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160 | |
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161 | Node root() { |
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162 | return r; |
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163 | } |
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164 | |
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165 | }; |
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166 | |
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167 | } |
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168 | |
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169 | #endif |
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170 | |
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171 | |
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