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