1 | // -*- mode:c++ -*- |
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2 | |
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3 | #ifndef EDMONDS_KARP_HH |
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4 | #define EDMONDS_KARP_HH |
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5 | |
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6 | #include <queue> |
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7 | |
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8 | //#include <marci_property_vector.hh> |
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9 | |
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10 | #include <algorithm> |
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11 | |
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12 | //#include <bfs_iterator.hh> |
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13 | |
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14 | namespace marci { |
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15 | template <typename Graph, typename FlowMap, typename CapacityMap> |
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16 | typename FlowMap::ValueType maxFlow(Graph &G, |
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17 | FlowMap &f, |
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18 | CapacityMap &c, |
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19 | typename Graph::NodeIt s, |
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20 | typename Graph::NodeIt t) |
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21 | { |
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22 | typedef typename Graph::NodeIt NodeIt; |
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23 | typedef typename Graph::EachNodeIt EachNodeIt; |
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24 | typedef typename Graph::EdgeIt EdgeIt; |
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25 | typedef typename Graph::EachEdgeIt EachEdgeIt; |
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26 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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27 | typedef typename Graph::InEdgeIt InEdgeIt; |
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28 | typedef typename FlowMap::ValueType T; |
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29 | |
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30 | T flow_val = 0; |
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31 | T aug_val; |
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32 | |
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33 | for(EachEdgeIt e(G);G.valid(e);G.goNext(e)) |
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34 | f.set(e,0); |
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35 | |
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36 | std::queue<NodeIt> bfs_queue; |
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37 | typename Graph::NodeMap<int> visited(G); //0: unvisited, |
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38 | //1: reached by a forward edge |
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39 | //2: reached by a backward edge |
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40 | //3: it is node s |
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41 | typename Graph::NodeMap<EdgeIt> tree(G); |
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42 | |
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43 | NodeIt gn; //FIXME: it might be too global for some people... |
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44 | |
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45 | augment: |
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46 | |
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47 | for(EachNodeIt n(G);G.valid(n);G.goNext(n)) |
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48 | visited.set(n,0); |
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49 | |
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50 | visited.set(s,3); |
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51 | |
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52 | //There must be a better way to do this: |
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53 | while(!bfs_queue.empty()) bfs_queue.pop(); |
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54 | |
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55 | bfs_queue.push(s); |
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56 | |
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57 | while(!bfs_queue.empty() && !visited.get(t)) |
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58 | { |
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59 | NodeIt n(bfs_queue.front()); |
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60 | bfs_queue.pop(); |
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61 | for(OutEdgeIt e(G,n);G.valid(e);G.goNext(e)) |
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62 | if(f.get(e)<c.get(e) && //FIXME: < |
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63 | !visited.get(G.bNode(e))) |
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64 | { |
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65 | NodeIt nn(G.bNode(e)); //It improves nothing |
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66 | tree.set(nn,e); |
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67 | visited.set(nn,1); |
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68 | bfs_queue.push(nn); |
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69 | } |
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70 | for(InEdgeIt e(G,n);G.valid(e);G.goNext(e)) |
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71 | if(f.get(e)>0 && //FIXME: > |
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72 | !visited.get(G.bNode(e))) |
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73 | { |
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74 | NodeIt nn(G.bNode(e)); |
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75 | tree.set(nn,e); |
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76 | visited.set(nn,2); |
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77 | bfs_queue.push(nn); |
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78 | } |
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79 | } |
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80 | |
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81 | if(!visited.get(t)) return flow_val; |
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82 | |
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83 | // Augmenting value computation |
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84 | aug_val = visited.get(t)==1 ? |
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85 | c.get(tree.get(t))-f.get(tree.get(t)) : f.get(tree.get(t)); |
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86 | //FIXME: I would need 'G.opposite(e,n)' |
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87 | gn = visited.get(t)==1 ? G.tail(tree.get(t)) : G.head(tree.get(t)); |
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88 | while(gn!=s) if(visited.get(gn)==1) |
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89 | { |
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90 | //FIXME: nonstandard gcc extension! |
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91 | aug_val <?= c.get(tree.get(gn))-f.get(tree.get(gn)); |
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92 | gn=G.tail(tree.get(gn)); |
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93 | } |
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94 | else { |
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95 | //FIXME: nonstandard gcc extension! |
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96 | aug_val <?= f.get(tree.get(gn)); |
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97 | gn=G.head(tree.get(gn)); |
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98 | } |
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99 | |
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100 | // The augmentation itself |
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101 | gn = t; |
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102 | while(gn!=s) if(visited.get(gn)==1) |
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103 | { |
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104 | f.set(tree.get(gn),f.get(tree.get(gn))+aug_val); |
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105 | gn=G.tail(tree.get(gn)); |
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106 | } |
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107 | else { |
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108 | f.set(tree.get(gn),f.get(tree.get(gn))-aug_val); |
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109 | gn=G.head(tree.get(gn)); |
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110 | } |
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111 | |
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112 | flow_val+=aug_val; |
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113 | |
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114 | goto augment; // Vivat goto forever! |
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115 | } |
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116 | |
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117 | } // namespace marci |
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118 | |
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119 | #endif //EDMONDS_KARP_HH |
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